Delayed release drug formulation

ABSTRACT

In a delayed release formulation comprising a core containing a drug and a delayed release coating for providing intestinal release, release of the drug in the colon is accelerated by including an isolation layer between the core and the delayed release coating. The delayed release coating comprises an inner layer and an outer layer. The outer layer comprises a pH dependently soluble polymeric material which has a pH threshold at about pH 5 or above. The inner layer comprises a soluble polymeric material which is soluble in intestinal fluid or gastrointestinal fluid, said soluble polymeric material being selected from the group consisting of a polycarboxylic acid polymer that is at least partially neutralised, and a non-ionic polymer, provided that, where said soluble polymeric material is a non-ionic polymer, said inner layer comprises at least one additive selected from a buffer agent and a base.

The present invention relates to a delayed release formulation with acore comprising a drug and a coating for providing delaying release ofthe drug until the colon. In particular, it relates to use of anisolation layer to accelerate initial release of the drug once theintestine is reached.

The targeting of drugs to the intestine is well known and has been knownfor over one hundred years. Commonly, the target of the drugs is thesmall intestine although the colon can be utilised as a means ofachieving local therapy or systemic treatment. The requirements for thecoatings on the drugs are different depending on the target site. Inorder to reach the colon, it is necessary for the drugs to pass throughthe small intestine, and therefore it is a requirement that a delayedrelease coating intended to release the drug in the colon does notrelease the drug in the small intestine.

Coated products for release in the small intestine commonly use polymercoatings which dissolve or disintegrate in a pH dependent manner. In thelow pH environment of the stomach, the polymer coating is insoluble.However, on reaching the small intestine, the pH rises to 5 and aboveand the polymeric coating dissolves or disintegrates. A commonly usedcoating is one containing ionisable carboxylic groups. At higher pHlevels, the carboxylic groups ionize, allowing the polymer coatings todisintegrate or dissolve. Common polymers of this type which are usedinclude Eudragit® L and Eudragit® S.

Various methods of improving the release in the small intestine byensuring an earlier release of the drug are known. US2008/0200482 is oneof a number of references which discloses partially neutralizing thecarboxylic groups in order to reduce the pH at which disintegrationoccurs. WO2008/135090 discloses a tablet with an inner coat of partiallyneutralized material and an outer coat with less or no neutralization.This is said to result in disintegration at an earlier time point whentransferred from the stomach.

Release of drugs in the colon typically requires an alternativeapproach. The colon is susceptible to a number of disease states,including inflammatory bowel disease, irritable bowel syndrome,constipation, diarrhoea, infection and carcinoma. In such conditions,drug targeting to the colon would maximise the therapeutic effectivenessof the treatment.

The colon can also be utilised as a portal for the entry of drugs intothe systemic circulation. Various formulations have been developed forcolonic drug delivery, including pro-drugs as well as formulated dosageforms, with the latter being more popular since the concept once provedcan be applied to other drugs.

The higher bacterial population in the colon has also been exploited indeveloping colonic drug delivery dosage forms through the use, ascarrier materials, of naturally occurring polysaccharides thatconstitute substrates for the numerous enzymes of the resident colonicbacteria. These materials are able to pass through the uppergastrointestinal regions intact but are digested upon entry into thecolon. Those studied so far include amylose, pectin, chitosan andgalactomannan.

One major attraction of using polysaccharides in this bacterial enzymeapproach to colonic drug delivery is that materials used are of foodgrade and so would be safe for use in humans. They are usually appliedas coatings or incorporated in the core material as a matrix carrier,and their digestion on entry into the colon by the colonic bacterialenzymes leads to the release of the drug load. An example of such aformulation, which employs an amylose coating, is disclosed inEP0343993A (BTG International Limited).

EP0502032A (British Technology Group Ltd) teaches the use of an outercoating comprising a film forming cellulose or acrylate polymer materialand amorphous amylose for a tablet comprising an active compound. Thepolymer material used is a pH independent release polymer material.

An article in Journal of Controlled Release (Milojevic et al; 38;(1996); 75-84) reports the results of investigations concerning theincorporation of a range of insoluble polymers into an amylose coatingin order to control amylose swelling. A range of cellulose and acrylatebased co-polymers are assessed, and a commercially available ethylcellulose (Ethocel®) is found to control the swelling most effectively.A pH dependent soluble coating of Eudragit® L100 is employed but only ina multi-layer system comprising a bioactive coated with an inner coatingof amylose and then an outer coating of Eudragit® L100.

A further amylose-based coating composition is disclosed in WO99/21536A(BTG International Limited). The coating composition comprises a mixtureof amylose and a water insoluble pH independent film-forming polymerwhich is formed from a water-insoluble cellulosic or acrylate polymermaterial.

WO99/25325A (BTG International Limited) also discloses a delayed releasecoating comprising amylose and (preferably) ethyl cellulose oralternatively an insoluble acrylate polymer. The coating compositionalso includes a plasticiser and the method finds particular applicationin the preparation of dosage forms comprising active materials that areunstable at temperatures in excess of 60° C., as the composition isformed at lower temperatures than this.

WO03/068196A (Alizyme Therapeutics Ltd) discloses a specific delayedrelease coating for the bioactive prednisolone sodium metasulphobenzoatecomprising glassy amylose, ethyl cellulose and dibutyl sebacate.

The use of polysaccharides other than amorphous amylose in a delayedrelease coating is disclosed in GB2367002 (British Sugar PLC). Examplesinclude guar gum, karaya gum, gum tragacanth and xanthan gum.Microparticles of these polysaccharides are dispersed in awater-insoluble film-forming polymer matrix formed for example from acellulose derivative, an acrylic polymer or a lignin.

WO01/76562A (Tampereen Patenttitoimisto Oy) discloses a per oralpharmaceutical formulation containing a drug and a chitosan (apolysaccharide obtained from chitin) for controlling its release. Thedrug and the chitosan are mixed into a homogeneous mechanical powdermixture which is granulated and then optionally tableted. Thegranulation may be performed with an enteric polymer (such as acopolymer of methacrylic acid) or the granules may be provided with aporous enteric coating.

WO2004/052339A (Salvona LLC) discloses a pH dependent drug releasesystem which is a free-flowing powder of solid hydrophobic nano-spherescomprising a drug encapsulated in a pH-sensitive micro-sphere. Thenano-spheres are formed from the drug in combination with a waxmaterial, and the pH-sensitive micro-sphere formed from a pH-sensitivepolymer (such as a Eudragit® polymer) in combination with awater-sensitive material such as a polysaccharide.

An article in the European Journal of Pharmaceutical Sciences (Akhgariet al; 28; March 2006; 307-314) reports the results of investigationsinto the use of certain polymethacrylate polymers to, inter alia,control the swelling of inulin. The polymethacrylate polymers testedwere Eudragit® RS; Eudragit® RL; 1:1 mixtures of Eudragit® RS andEudragit® RL; Eudragit® FS; and 1:1 mixtures of Eudragit® RS andEudragit® S.

U.S. Pat. No. 5,422,121 (Röhm GmbH) discloses an oral dosage form havinga core containing at least one active ingredient enclosed within a shellmaterial which comprises a polysaccharide that decomposes in the colonin admixture with a film-forming polymer. The ratio by weight ofpolysaccharide to film forming polymer is from 1:2 to 5:1, preferablyfrom 1:1 to 4:1. Premature diffusion of the active ingredient from thecore can be suppressed using a gastric resistant isolating layer. Thereference exemplifies inter alia tablets having an inner isolating layerof Eudragit® L30D with an outer layer comprising Eudragit® L30D and guargum (Example 2).

WO96/36321A discloses an oral dosage form comprising a core containingbisacodyl, and an enteric polymer coating for the core, the coatingcomprising at least one inner coating layer and an outer coating layer.The or each the inner coating layer is an enteric polymer that begins todissolve in an aqueous medium at a pH from about 5 to about 6.3, and theouter coating layer is an enteric polymer that begins to dissolve in anaqueous medium at a pH from about 6.8 to about 7.2. The enteric polymercoating materials for the inner layer(s) are selected from the groupconsisting of cellulose acetate phthalate; cellulose acetatetrimellitate; hydroxypropyl methylcellulose phthalate; hydroxypropylmethylcellulose acetate succinate; polyvinyl acetate phthalate;poly(methacrylic acid, methyl methacrylate) 1:1; poly(methacrylic acid,ethyl acrylate) 1:1; and compatible mixtures thereof.

An abstract entitled “An investigation of combined pH-andbacterially-triggered oral colon targeted drug delivery system” by HeiniKari of the Department of Pharmaceutical Technology in the Faculty ofPharmacy at University of Helsinki dated 2 Sep. 2009 discloses tabletformulations having a heat treated polysaccharide/Eudragit® S coatingfor colonic release and an HPMC sub-coating. Very few details of theformulations are provided in the abstract. For example, the identity ofthe polysaccharide, the proportions of the polysaccharide and Eudragit®S in the coating and the identity and proportions of any excipients arenot provided. However, it is disclosed that tablets with heat treatedcoatings, and especially with HPMC sub-coatings, had “better” drugrelease profiles than completely organic coatings in the conventionaldissolution tests in the presence of one enzyme. No details of how orwhy the drug release profile is better are provided although the authorspeculates that the reason may be because of a more uniform coatingstructure in which polysaccharide granules are not present.

In a paper entitled “A novel concept in enteric coating: Adouble-coating system providing rapid drug release in the proximal smallintestine” by Liu et al (J. Cont. Rel. 133 (2009) 119-124), it isdisclosed that release of prednisolone from tablets having a doublecoating system comprising an inner coat of partially neutralisedEudragit® L 30 D-55 and organic acid, and an outer coat of standardEudragit® L 30 D-55 was accelerated in conditions resembling the uppersmall intestine. The inner coat was neutralised to pH 5.6 in thepresence of 10% citric acid or adipic acid. The tablets did not have anisolation layer.

In a paper entitled “SEM/EDX and confocal microscopy analysis of noveland conventional enteric-coated systems” by Liu et al (Int. J. Pharm.369 (2009) 72-78), it is disclosed that prednisolone was released morerapidly from tablets coated with an inner coat of partially neutralisedEudragit® L 30 D-55 and organic acid, and an outer coat of standardEudragit® L 30 D-55, than from tablets coated with Eudragit® L 30 D-55alone with or without a subcoat of HPMC. The double coated tablets didnot have a subcoat of HPMC although the authors of the paper observedthat drug release from the tablets having the single enteric coat withthe HPMC subcoat was faster than from the single enteric coated tabletswithout the subcoat.

It is also reported in a paper entitled “A novel double-coating approachfor improved pH-triggered delivery to the ileo-colonic region of thegastrointestinal tract” by Liu et al (Eur. J. Pharm. Biopharm. 74 (2010)311-315), that initial release in vitro (in Krebs buffer (pH 7.4) after2 h in 0.1 M HCl) of prednisolone was faster from tablets coated with acoating system comprising an inner layer of partially neutralisedEudragit S and buffer agent and an outer layer of standard Eudragit S,than from tablets without the inner layer. None of the tablets disclosedin this paper had an isolation layer.

WO2007/122374A discloses a colonic drug delivery formulation in which amixture of a pH dependent film forming polymeric material and apolysaccharide such as starch is used. Although it is known that thisformulation shows delayed release followed by a relatively quick releaseof the drug, it would be preferred if the drug release was even quickerin the colon, after the triggers are initiated.

In accordance with a first aspect of the present invention, there isprovided an isolation layer for use in accelerating drug release in theintestine of a subject from a delayed release drug formulation for oraladministration to said subject, said formulation comprising:

-   -   a core comprising said drug;    -   said isolation layer coating said core; and    -   an outer coating for providing intestinal release of said drug,        said outer coating comprising an outer layer and an inner layer,

wherein said outer layer comprises a pH dependently soluble polymericmaterial which has a pH threshold at about pH 5 or above, and

wherein the inner layer comprises a soluble polymeric material which issoluble in intestinal fluid or gastrointestinal fluid, said solublepolymeric material being selected from the group consisting of apolycarboxylic acid polymer that is at least partially neutralised, anda non-ionic polymer, provided that, where said soluble polymericmaterial is a non-ionic polymer, said inner layer comprises at least oneadditive selected from a buffer agent and a base.

The Inventors have discovered that the use of an isolation layer in suchformulations accelerates initial release of the drug once theformulations are exposed to pH conditions found in the colon. Thisresult was entirely unexpected. The Inventors introduced the isolationfor the purpose of preventing erosion at the edges of the tablets priorto coating. They fully expected the additional layer to further delayrelease in line with conventional wisdom. However, they were surprisedto observe that, rather than delay initial release, the isolation layeractually accelerated initial once the coated tablets were exposed tocolonic pH. The Inventors are not aware of any literature which couldhave predicted such a result.

The isolation layer also improves the stability of the formulationsduring storage by preventing deceleration of initial release over time.

In preferred embodiments, the isolation layer comprises a film-formingnon-ionic polymer, such as HPMC or PVA, and typically has a thicknessfrom about 1 mg polymer/cm² to about 5 mg polymer/cm².

In some preferred embodiments, the pH dependently soluble polymericmaterial is the sole film forming polymer in the outer layer. However,in other preferred embodiments, the outer layer has a mixture of adigestible (or “first”) polymeric material susceptible to attack bycolonic bacteria, e.g. a polysaccharide, and the pH dependently soluble(or “second”) polymeric material.

The soluble (or “third”) polymeric material that is soluble inintestinal fluid or gastrointestinal fluid is typically a partially orfully neutralised polycarboxylic acid polymer. In these embodiments, thepH dependently soluble (or second) polymer material is typically apolycarboxylic acid polymer of the same type as the polymer of the innerlayer but either non-neutralised or partially neutralised to a lowerextent than the soluble (or third) polymeric material.

Formulations according to embodiments of the present invention havesuperior colonic-release properties over comparative coatings designedfor site-specific release in the colon. In this connection, drug releasefrom formulations according to embodiments of the present inventionappears to be accelerated in the colon when compared to comparativecolonic release formulations. The Inventors are confident that otherformulations within the scope of the invention should also have superiorrelease properties over comparative coatings designed for site-specificrelease in the small intestine, and proximal small intestine inparticular. Broadly speaking, the region of the intestine in whichinitial release occurs can be controlled by the choice of pH dependentlysoluble polymeric material.

Without wishing to be bound by any particular theory, the Inventorsbelieve that, once intestinal fluid or gastrointestinal fluid penetratesthe outer layer, the inner layer begins to dissolve before the outerlayer to form a fluid region between the core and the outer layer. Thefluid region not only facilitates dissolution and/or disintegration ofthe outer layer from the inside, but also softens and begins to break upthe core so that, when the outer layer degrades, the drug is releasedfrom the core more quickly.

In some preferred embodiments, the further acceleration provided by theisolation layer is very likely due to the barrier effect between anacidic core (e.g. a core containing 5ASA) and an alkaline inner layer.In these embodiments, the Inventors believe that the isolation layerprevents or limits the effect of the acidic drug on the alkaline innerlayer, not compromising and/or competing for the alkalinity whichpromotes the accelerated dissolution of the outer layer.

It is preferred that the digestible (or first) polymeric materialcomprises at least one polysaccharide selected from the group consistingof starch; amylose; amylopectin; chitosan; chondroitin sulphate;cyclodextrin; dextran; pullulan; carrageenan; scleroglucan; chitin;curdulan and levan. It is particularly preferred that the digestible (orfirst) polymeric material is starch.

In preferred embodiments, the pH dependently soluble (or second)polymeric material is an anionic polymeric material, and more preferablyan anionic copolymer of a (meth)acrylic acid and a (meth)acrylic acidalkyl ester.

The soluble (or third) polymeric material of the inner layer ispreferably an anionic polymeric material and more preferably an at leastpartially neutralised, preferably fully neutralised, copolymer of a(meth)acrylic acid and a (meth)acrylic acid alkyl ester.

In a preferred embodiment, the second polymeric material is the sametype of copolymer of a (meth)acrylic acid and a (meth)acrylic acid alkylester as the third polymeric material prior to neutralisation.

In a particularly favourable embodiment, the present invention relatesto a delayed release drug formulation comprising a core comprising adrug, an isolation layer for the core and a delayed release coating forthe isolated core, the delayed release coating comprising an outer layerand an inner layer, wherein the outer layer comprises a mixture ofstarch and a copolymer of a (meth)acrylic acid and a (meth)acrylic acidC₁₋₄ alkyl ester; and the inner layer comprises a fully neutralizedcopolymer of a (meth)acrylic acid and a (meth)acrylic acid C₁₋₄ alkylester.

Some materials that are susceptible to attack by colonic bacteria, e.g.amylose, swell when exposed to aqueous fluid, e.g. gastrointestinalfluid. Such swelling is undesirable since it results typically inpremature release of the drug. The swelling is controlled by theinclusion of a pH dependent material having a pH threshold of pH 5 orabove.

A further technical advantage of the present invention (compared, forexample, to the formulation disclosed in WO01/76562A) is thatsubstantially no drug is released for an extended period (that is,whilst the coating is intact and is being dissolved/disintegrated),following which the drug is released relatively quickly. This is incontrast to homogeneous tablets from which the drug release profile isgradual from the outset rather than delayed then pulsatile.

A yet further technical advantage of the present invention compared toWO2007/122374A is accelerated release of the drug once the formulationis exposed to the conditions of the colonic environment.

Isolation Layer

The isolation layer typically accelerates initial release of the drug inthe intestine from the present formulation compared to an equivalentformulation without the isolation layer.

By “accelerating release”, the Inventors mean reducing the delay beforeinitial release of the drug once exposed to intestinal conditions. Thisdelay is referred to as the lag time or T_(lag).

The present invention has particular application in accelerating releasein the colon. According to these embodiments of the present invention,the lag time (T_(lag)) in vitro in Krebs buffer at pH 7.4 after 2 h at0.1M HCl is typically reduced by at least 10%, preferably by at least20%, more preferably by at least 30% and most preferably by at least40%. In absolute terms, the lag time (T_(lag)) in vitro in Krebs bufferat pH 7.4 after 2 h at 0.1M HCl is typically reduced by at least 10minutes, preferably by at least 20 minutes, more preferably by at least30 minutes, and most preferably by at least 45 minutes.

In other embodiments, the isolation layer is for use in acceleratingdrug release in the small intestine, and particularly in the proximalsmall intestine, of the subject. According to these embodiments of thepresent invention, the lag time (T_(lag)) in vitro in a bufferedsolution at an appropriate pH (e.g. pH 5.5 for the proximal smallintestine or pH 6.8 to 7.2 for the ileum) after 2 h at 0.1M HCl istypically similar to that indicated above at pH 7.4.

The polymeric material of the isolation layer is preferably present inthe isolation layer in a total amount from about 1 mg polymer/cm² toabout 5 mg polymer/cm², preferably from about 2 mg polymer/cm² to about4 mg polymer/cm², more preferably from about 2.5 mg polymer/cm² to about3.5 mg polymer/cm², and most preferably of about 3 mg polymer/cm², assuch coating amounts tend to provide optimum improvement in accelerationof initial release.

The thickness of the isolation layer is typically from about 5 μm toabout 100 μm, preferably from about 10 μm to about 60 μm, and mostpreferably from about 20 μm to about 40 μm. Such coating thicknessestypically provide optimum improvement in acceleration of initialrelease.

By “thickness” of a layer or coating, the Inventors are referring to theperpendicular dimension between the inner and outer surfaces of thelayer or coating in question. The values provided herein regarding layeror coating thickness are a mean average of the thickness measured atdifferent points of a cross-section of the coated dosage form, includingat the edges where the layer or coating is typically thinner.

The thickness of a layer or coating on an oral dosage form such as atablet, is generally measured by subjecting the cross section of thedosage form to scanning electron microscopy (SEM) and then by using themeasurement software of the SEM instrument (i.e. Phenom SEM measurementsoftware) or any other measurement software like MeasureIT from OlympusSoft Imaging Solutions GmbH. However, SEM may not be specific enough insome cases, including in cases where adjacent layers cannot bedistinguished properly, or where the typical margin of error in SEM(about 5 to 10%) is not acceptable. In such cases, the thickness of thecoating or layer to be distinguished can be determined precisely usingatomic force microscopy (AFM) or terahertz pulsed spectroscopy andimaging (TPI). A method of using TPI to measure the thickness of a layerin a tablet is described in the Journal of Pharmacy and Pharmacology(2007), 59: 209-223.

As indicated above, the isolation layer typically comprises at least onenon-ionic polymer. Suitable polymers include at least one polymerselected from the group consisting of methylcellulose (MC);hydroxypropyl cellulose (HPC); hydroxypropyl methylcellulose (HPMC);poly(ethylene oxide)-graft-polyvinyl alcohol; polyvinylpyrollidone(PVP); and polyvinyl alcohol (PVA).

In some embodiments, the isolation layer does not need to include aplasticizer. However, in other embodiments, the isolation layer canadditionally comprise at least one plasticizer to provide better filmquality. Any suitable plasticizers may be used, including triethylcitrate (TEC) and polyethylene glycol (PEG). The total amount ofplasticizer(s) in the layer is typically from about 5 wt % to about 50wt %, e.g. from about 10 wt % to about 30 wt %. In some embodiments, thetotal amount of plasticizer may be about 20 wt %.

In some preferred embodiments, the isolation layer comprises HPMC. Inother preferred embodiments, the isolation layer comprises PVA.

The non-ionic polymer is typically present in the isolation layer as thesole film-forming polymeric material.

Digestible (or First) Polymeric Material

The digestible (or first) polymeric material typically comprises apolysaccharide, preferably containing a plurality of hexose units. In apreferred embodiment, the polysaccharide is at least one polysaccharideselected from the group consisting of starch; amylose; amylopectin;chitosan; chondroitin sulphate; cyclodextrin; dextran; pullulan;carrageenan; scleroglucan; chitin; curdulan and levan. It is furtherpreferred that the polysaccharide is starch, amylose or amylopectin,most preferably starch.

The person skilled in the art is capable of determining whether apolymeric material is susceptible to attack by colonic bacteria usingtechniques comprising part of the common general knowledge. For example,a pre-determined amount of a given material could be exposed to an assaycontaining an enzyme from a bacterium found in the colon and the changein weight of the material over time may be measured.

The polysaccharide is preferably starch. Starches are usually extractedfrom natural sources such as cereals; pulses; and tubers. Suitablestarches for use in the present invention are typically food gradestarches and include rice starch; wheat starch; corn (or maize) starch;pea starch; potato starch; sweet potato starch; tapioca starch; sorghumstarch; sago starch; and arrow root starch. The use of maize starch isexemplified below.

Starch is typically a mixture of two different polysaccharides, namelyamylose and amylopectin. Different starches may have differentproportions of these two polysaccharides. Most natural (unmodified)maize starches have from about 20 wt % to about 30 wt % amylose with theremainder being at least substantially made up of amylopectin. Starchessuitable for use in the present invention typically have at least 0.1 wt%, e.g. at least 10% or 15%, preferably at least 35 wt %, amylose.

“High amylose” starches, i.e. starches having at least 50 wt amylose,are suitable. Particularly suitable starches have from about 55 wt % toabout 75 wt %, e.g. about 60 wt % or about 70 wt % amylose. Inparticular, starches having from about 50 wt % to about 60 wt % amyloseare also suitable,

Starches suitable for use in the present invention may have up to 100%amylopectin, more typically from about 0.1 wt % to about 99.9 wt %amylopectin. “Low amylose” starches, i.e. starches having no more than50 wt % amylose and at least 50 wt % amylopectin, e.g. up to 75 wt %amylopectin and even as much as up to 99 wt % amylopectin, are stillsuitable. The starch may be, for example, unmodified waxy corn starch.This typically comprises about 100% amylopectin.

Preferred starches have no more than 50 wt % amylopectin. As indicatedabove, particularly suitable starches are “high amylose” starches whichhave from about 25 wt % to about 45 wt % amylopectin, e.g. about 30 wt %or about 40 wt % amylopectin. In particular, starches having from about40 wt % to about 50 wt % amylopectin are also suitable.

The person skilled in the art is capable of determining the relativeproportions of amylose and amylopectin in any given starch. For example,near-infrared (“NIR”) spectroscopy could be used to determine theamylose and amylopectin content of a starch using calibration curvesobtained by NIR using laboratory-produced mixtures of known amounts ofthese two components. Further, starch could be hydrolysed to glucoseusing amyloglucosidase. A series of phosphorylation and oxidationreactions catalysed by enzymes result in the formation of reducednicotinamide adenine dinucleotide phosphate (“NADPH”). The quantity ofNADPH formed is stoichiometric with the original glucose content.Suitable test kits for this procedure are available (e.g., R-BiopharmGmbH, Germany). Another method that could be used involves subjectingthe coating to digestion by bacterial enzymes, e.g. α-amylase, toproduce short chain fatty acids (“SCFA”) which can be quantified bygas-liquid chromatography using a capillary column.

Preferred starches have amylose in its glassy form although amylose inits amorphous form may also be used in conjunction with the presentinvention.

Preferred starches are “off-the-shelf” starches, i.e. starches whichrequire no processing prior to use in the context of the presentinvention. Examples of particularly suitable “high amylose” starchesinclude Hylon™ VII (National Starch, Germany), Eurylon™ 6 (or VI) orAmylo NI-460 or Amylo N-400 (Roquette, Lestrem, France), or Amylogel03003 (Cargill, Minneapolis, USA) all of which are examples of a maizestarch having from about 50 wt % to about 75 wt % amylose.

pH Dependently Soluble (or Second) Polymeric Material

The present invention involves the use of a pH dependently soluble (orsecond) polymeric material that dissolves in a pH dependent manner. Thesecond material is a film forming polymer that is pH sensitive, i.e. hasa “pH threshold” which is the pH below which it is insoluble in aqueousmedia and at or above which it is soluble in aqueous media. Thus, the pHof the surrounding medium triggers dissolution of the second polymericmaterial and none (or essentially none) of the second polymeric materialdissolves below the pH threshold. Once the pH of the surrounding mediumreaches (or exceeds) the pH threshold, the second polymeric materialbecomes soluble.

Throughout the specification, the term “insoluble” is used to mean that1 g of a polymeric material requires more than 10,000 ml of solvent or“surrounding medium” to dissolve at a given pH. In addition, the term“soluble” is used to mean that 1 g of a polymeric material requires lessthan 10,000 ml, preferably less than 5,000 ml, more preferably less than1000 ml, even more preferably less than 100 ml or 10 ml of solvent orsurrounding medium to dissolve at a given pH.

By “surrounding medium”, the Inventors mean gastric fluid and intestinalfluid, or an aqueous solution designed to recreate in vitro gastricfluid or intestinal fluid.

The normal pH of gastric juice is usually in the range of pH 1 to 3. Thesecond polymeric material is insoluble below pH 5 and soluble at aboutpH 5 or above and, thus, is usually insoluble in gastric juice. Such amaterial may be referred to as a gastro-resistant material or an“enteric” material.

The second polymeric material has a pH threshold of pH 5 or above, e.g.about pH 5.5 or above, preferably about pH 6 or above and morepreferably about pH 6.5 or above. The second polymeric materialtypically has a pH threshold of no more than about pH 8, e.g. no morethan about pH 7.5 and preferably no more than about pH 7.2. Preferably,the second polymeric material has a pH threshold within the range of pHfound in intestinal fluid. The pH of intestinal fluid may vary from oneperson to the next, but in healthy humans is generally from about pH 5to 6 in the duodenum, from about 6 to 8 in the jejunum, from about 7 to8 in the ileum, and from about 6 to 8 in the colon.

For embodiments in which initial release is intended for the smallintestine, the second polymeric material preferably has a pH thresholdof about pH 5.5, and more preferably has a pH threshold of about pH 6.For embodiments in which initial release is intended for the colon, thesecond polymeric material preferably has a pH threshold of about pH 6.5,and more preferably has a pH threshold of about pH 7.

The pH threshold at which a material becomes soluble may be determinedby a simple titration technique which would be part of the commongeneral knowledge to the person skilled in the art.

The second polymeric material is typically a film-forming polymericmaterial such as a polymethacrylate polymer, a cellulose polymer or apolyvinyl-based polymer. Examples of suitable cellulose polymers includecellulose acetate phthalate (CAP); cellulose acetate trimellitate (CAT);Hydroxypropylmethylcellulose phthalate (HPMCP) andhydroxypropylmethylcellulose acetate succinate (HPMC-AS). Examples ofsuitable polyvinyl-based polymers include polyvinyl acetate phthalate(PVAP).

The second material is preferably an “anionic” polymeric material, i.e.a polymeric material containing groups that are ionisable in aqueousmedia to form anions (see below), and more preferably a co-polymer of a(meth)acrylic acid and a (meth)acrylic acid C₁₋₄ alkyl ester, forexample, a copolymer of methacrylic acid and methacrylic acid methylester. Such a polymer is known as a poly(methacrylic acid/methylmethacrylate) co-polymer. Suitable examples of such co-polymers areusually anionic and not sustained release polymethacrylates. The ratioof carboxylic acid groups to methyl ester groups (the “acid:esterratio”) in these co-polymers determines the pH at which the co-polymeris soluble. The acid:ester ratio may be from about 2:1 to about 1:3,e.g. about 1:1 or, preferably, about 1:2. The molecular weight (“MW”) ofpreferred anionic co-polymers is usually from about 120,000 to 150,000g/mol, preferably about 125,000 g/mol or about 135,000 g/mol.

Preferred anionic poly(methacrylic acid/methyl methacrylate) co-polymershave a molecular weight of about 125,000 g/mol. Suitable examples ofsuch polymers have an acid:ester ratio of about 1:1 and a pH thresholdof about pH 6, or have an acid:ester ratio of about 1:2 and a pHthreshold of about pH 7.

A specific example of a suitable anionic poly(methacrylic acid/methylmethacrylate) co-polymer having a molecular weight of about 125,000g/mol, an acid:ester ratio of about 1:1 and a pH threshold of about pH 6is sold under the trade mark Eudragit® L. This polymer is available inthe form of a powder (Eudragit® L 100), or as an organic solution(12.5%) (Eudragit® L 12.5).

A specific example of a suitable anionic poly(methacrylic acid/methylmethacrylate) co-polymer having a molecular weight of about 125,000g/mol, an acid:ester ratio of about 1:2 and a pH threshold of about pH 7is sold under the trade mark Eudragit® S. This polymer is available inthe form of a powder (Eudragit® S 100) or as an organic solution (12.5%)(Eudragit® S 12.5).

The second polymeric material may be a co-polymer of methacrylic acidand ethyl acrylate. Preferred poly(methacrylic acid/ethyl acrylate)co-polymers have a molecular weight from about 300,000 to 350,000 g/mol,e.g. about 320,000 g/mol. Suitable examples of such co-polymers have anacid:ester ratio of about 1:1 and a pH threshold of about pH 5.5.

A specific example of a suitable anionic poly(methacrylic acid/ethylacrylate) co-polymer is available in the form of a powder and sold underthe trade mark Eudragit® L 100-55, or in the form of an aqueousdispersion (30%) and sold under the trade mark Eudragit® L 30 D-55.

The second polymeric material may be a co-polymer of methyl acrylate,methyl methacrylate and methacrylic acid. Preferred poly(methylacrylate/methyl methacrylate/methacrylic acid) co-polymers have amolecular weight from about 250,000 to about 300,000 g/mol, e.g. about280,000 g/mol. Suitable examples of such co-polymers have a methylacrylate:methyl methacrylate:methacrylic acid ratio of about 7:3:1thereby providing an acid:ester ratio of about 1:10 and a pH thresholdof about pH 7.

A specific example of a suitable anionic poly(methyl acrylate/methylmethacrylate/ethyl acrylate) co-polymer is available in the form of anaqueous dispersion (30%) and is sold under the trade mark Eudragit® FS30D.

The Eudragit® co-polymers are manufactured and/or distributed by EvonikGmbH, Darmstadt, Germany.

Mixtures of film forming polymer materials may be used as appropriate.For example, the second polymeric material may be a blend of at leasttwo different polymers having a pH threshold of about pH 5 and above.Preferably, the polymers in the blend are different polymethacrylatepolymers. In embodiments where the second polymeric material is a blendof two different polymers having a pH threshold of about pH 5 or above,the polymers may be present in the blend in a polymer weight ratio fromabout 1:99 to about 99:1, .e.g. from about 10:90 to about 90:10, or from25:75 to about 75:25, or from about 40:60 to about 60:40, for exampleabout 50:50.

An example of a suitable mixture would include a mixture, e.g. a 1:1mixture, of Eudragit® L and Eudragit® S. A further example would includea blend, e.g. a 50:50 blend, of Eudragit S and Eudragit FS.

For the avoidance of doubt, the terms “mixture” and “blend” in thecontext of mixtures or blends of polymers forming the second polymericmaterial, are used herein interchangeably.

However, the use of a particular film forming polymer material, e.g. apoly(methacrylic acid/methyl methacrylate) co-polymer, alone ispreferred. The use of Eudragit® S alone as the second polymeric materialis particularly preferred for colonic release formulations.

Outer Layer

In some preferred embodiments, the pH dependently soluble (or second)polymeric material(s) is/are present in the outer layer as the solefilm-forming polymeric material(s). In other preferred embodiments, thepH dependently soluble (or second) polymeric material(s) is/are presentin the outer layer in admixture with the digestible (or first) polymericmaterial(s) which is susceptible to attack by colonic bacteria.

In embodiments in which the outer layer comprises a mixture of first andsecond polymeric materials, the proportion of the first polymericmaterial to the second polymeric material is typically at least 1:99,e.g. at least 10:90 and preferably at least 25:75. The proportion istypically no more than 99:1, e.g. no more than 75:25 and preferably nomore than 60:40. In some embodiments, the proportion may be no more than35:65. In some preferred embodiments, the proportion is from 10:90 to75:25, e.g. from 10:90 to 60:40 and preferably from 25:75 to 60:40. Insome particularly preferred embodiments, the proportion is from 15:85 to35:65, e.g. from 25:75 to 35:65 and preferably about 30:70. In otherparticularly preferred embodiments, the proportion is from 40:60 toabout 60:40, e.g. about 50:50.

The mixture of first and second polymeric materials is preferablysubstantially homogenous.

Optionally, conventional excipients such as those excipients selectedfrom plasticisers for film formation (for example, triethyl citrate),anti-tack agents (such as glyceryl monostearate or GMS) and surfactants(such as polysorbate 80), may be included in amounts up to 30 wt % ofthe final composition of the outer coating preparation.

The thickness of the outer coating of the core is typically from about10 μm to about 150 μm. The thickness of a specific coating will,however, depend on the composition of the coating. For example, coatingthickness is directly proportional to the amount of polysaccharide inthe coating. Thus, in embodiments where the coating comprises highamylose starch and Eudragit™ S at a ratio of about 30:70, the coatingthickness may be from about 70 μm to about 130 μm, and preferably fromabout 90 μm to about 110 μm.

The coating amount of the polymeric material(s) in the outer coating istypically from about 2 mg/cm² to about 10 mg/cm², preferably from about2 mg/cm² to about 8 mg/cm², and most preferably from about 4 mg/cm² toabout 8 mg/cm², based on the dry weight of the total polymeric material.These values are particularly appropriate for cores having a diameterfrom about 5×10⁻⁴ m to about 25 mm.

Soluble (or Third) Polymeric Material

The formulation according to the present invention additionally has aninner layer which is positioned between the isolation layer and theouter layer. The inner layer comprises a third polymeric material whichmay be insoluble in gastric fluid and soluble in intestinal fluid, butpreferably is soluble in both gastric fluid and intestinal fluid(referred herein as gastrointestinal fluid).

By “gastric fluid”, the inventors mean the aqueous fluid in the stomachof a mammal, particularly a human. The fluid contains up to about 0.1 Nhydrochloric acid and substantial quantities of potassium chloride andsodium chloride, and plays a key role in digestion by activatingdigestive enzymes and denaturing ingested protein. Gastric acid isproduced by cells lining the stomach and other cells produce bicarbonatewhich acts as a buffer to prevent the gastric fluid from becoming tooacidic.

By “intestinal fluid”, the Inventors mean the fluid in the lumen of theintestine of a mammal, particularly a human. Intestinal fluid is a paleyellow aqueous fluid secreted from glands lining the walls of theintestine. Intestinal fluid includes fluid found in the small intestine,i.e. fluid found in the duodenum (or “duodenal fluid”), fluid found inthe jejunum (or “jejunal fluid”) and fluid found in the ileum (or “ilealfluid”), and fluid found in the large intestine, e.g. “colonic fluid”.

The skilled person can readily determine whether a polymer is soluble ingastric fluid and/or intestinal fluid. If a polymer is soluble in water(or aqueous solution), e.g. a buffer solution) at a pH from 1 to 3, thenthat polymer would typically be soluble in gastric fluid. Similarly if apolymer is soluble in water (or aqueous solution, e.g. a buffersolution) at a pH from 5 to 8, then that polymer would typically besoluble in intestinal fluid. Alternatively, the compositions of gastricfluid and intestinal fluid are known and may be replicated in vitro. Ifa polymer is soluble in artificial gastric fluid or intestinal fluid invitro, then it would typically be soluble in gastric fluid or intestinalfluid respectively in vivo.

Any pharmacologically acceptable water soluble film forming polymersare, in principle, suitable for use as the third polymeric material. Thesolubility of the water soluble polymers may be dependent on pH, i.e.the third polymeric material may be a pH sensitive polymer having a pHthreshold. In such embodiments, the pH threshold of the third polymericmaterial is less than, typically at least 0.5 pH units less than andpreferably from 0.5 to 3.5 pH units less than, the pH threshold of thesecond polymeric material. The pH threshold of the third polymericmaterial is typically from about pH 4.5 to about pH 7.5.

The third polymeric material may be soluble in at least one fluidselected from gastric fluid, duodenal fluid, jejunal fluid and ilealfluid. However, in preferred embodiments, the solubility of the thirdpolymeric material in water is not dependent on pH; at least not withinthe range of pH found in the intestine. In preferred embodiments, thethird polymeric material is soluble in fluid at any point in the stomachand intestine, i.e. in gastrointestinal fluid.

Suitable polymers for use as the third polymeric material preferablycontain groups that are ionisable in aqueous media to form anions. Suchpolymers are known in the art as “anionic” polymers. Suitable anionicpolymers include polycarboxylic acid polymers, i.e. polymers orco-polymers that contain a plurality of carboxylic acid functionalgroups that are ionisable in aqueous media such as intestinal fluid, toform carboxylate anions.

In embodiments in which the third polymeric material is a polycarboxylicacid polymer, it is preferred that the third polymeric material is atleast partially neutralised, i.e. that at least a portion, e.g. at least10%, preferably at least 25%, more preferably at least 50%, and mostpreferably at least 90%, of the carboxylic acid groups in are the formof carboxylate anions. In particularly preferred embodiments, all of thecarboxylic acid groups in the third polymeric material are in the formof carboxylate anions. Such polymers are referred to herein as “fullyneutralised”.

In preferred embodiments, the second and third polymeric materials arebased on the same polycarboxylic acid polymer with the third polymericmaterial having a higher degree of neutralisation than the secondpolymeric material. For example, for a particular polycarboxylic acidpolymer, the second polymeric material may be in non-neutralised formwith the third polymeric material in partially or fully neutralisedform. Alternatively, the second polymeric material may be in partiallyneutralised form, with the third polymeric material also in partiallyneutralised form (although partially neutralised to a greater extent),or in fully neutralised form.

Examples of suitable polycarboxylic acid polymers include celluloseacetate phthalate (CAP), polyvinyl acetate phthalate (PVAP),hydroxypropyl methylcellulose phthalate (HPMCP), hydroxypropylmethylcellulose acetate succinate (HPMC-AS), cellulose acetatetrimellitate (CAT), xanthan gum, alginates and shellac. However, thepolycarboxylic acid polymer is preferably selected from co-polymers of a(meth)acrylic acid and a (meth)acrylic acid alkyl, e.g. C₁₋₄ alkyl,ester and a copolymer of methacrylic acid and methacrylic acid methylester is particularly suitable. Such a polymer is known as apoly(methacrylic acid/methyl methacrylate) co-polymer or a“polymethacrylate”. The ratio of carboxylic acid groups to methyl estergroups (the “acid:ester ratio”) in these co-polymers determines the pHat which the co-polymer is soluble. The acid:ester ratio may be fromabout 2:1 to about 1:3, e.g. about 1:1 or, preferably, about 1:2. Themolecular weight (“MW”) of preferred anionic co-polymers is usually fromabout 120,000 to 150,000, preferably about 125,000 or about 135,000.

Preferred co-polymers for the third polymeric material are discussed indetail in the section above relating to the second polymeric material,and include Eudragit® L; Eudragit® S; Eudragit® FS 30 D; Eudragit®L30D-55; and Eudragit® L100-55.

The exemplary polymers may be used as the third polymeric material innon-neutralised form (provided the pH threshold of the polymer is lessthan the pH threshold of the second polymeric material—see above) or maybe used in at least partially, more preferably fully, neutralised form.

Partially neutralised polymers suitable for use as the third polymericmaterial, and their methods of production, are known in the art, forexample from US2008/0200482A and WO2008/135090A. These polymers may befully neutralised by the addition of further base to the coatingsolutions.

In preferred embodiments, the third polymeric material is an at leastpartially, preferably fully, neutralised co-polymer of (meth)acrylicacid and a (meth)acrylic acid C₁₋₄ alkyl ester. In particularlypreferred embodiments, the third polymeric material is a fullyneutralised co-polymer of (meth)acrylic acid and (meth)acrylic acidmethyl ester, particularly Eudragit® S.

The Inventors have observed that fully neutralised Eudragit® S iscapable of forming a film and is readily and completely soluble in waterindependently of at least the range of pH found in the intestine, e.g.about pH 5 to about pH 8. Fully neutralised Eudragit® S is particularlypreferred for use as the third polymeric material in the presentinvention.

Other polymers suitable for use as the third polymeric material includepharmacologically acceptable non-ionic polymers, i.e. pharmacologicallyacceptable polymers which do not ionise in aqueous media. In theseembodiments, the inner layer additionally comprises at least oneadditive selected from a buffer agent and a base. In particular, theinner layer of these embodiments preferably comprises a base and,optionally, a buffer agent. In preferred embodiments, the inner layercomprises both a buffer agent and a base. Suitable examples of bufferagents and bases are discussed below.

Examples of suitable non-ionic polymers include methylcellulose (MC),hydroxypropyl cellulose (HPC), hydroxypropyl methylcellulose (HPMC),poly(ethylene oxide)-graft-polyvinyl alcohol, polyvinylpyrrolidinone(PVP) and polyvinyl alcohol (PVA).

Mixtures of film forming polymer materials may be used as appropriate.The polymer components in such mixtures may be anionic polymers,non-ionic polymers, or a mixture of anionic and non-ionic polymers. Anexample of a suitable mixture would include a mixture, e.g. a 1:1mixture, of Eudragit® L and Eudragit® S, and a mixture, e.g. a 1:1mixture, of Eudragit® S and HPMC. However, the use of a particular filmforming polymeric material alone, e.g. a poly(methacrylic acid/methylmethacrylate) co-polymer and Eudragit® S in particular, is preferred.

Base

In preferred embodiments, the inner layer comprises at least one base.The purpose of the base is to provide an alkaline environment on theunderside of the outer layer once intestinal fluid begins to penetratethe outer layer. Without being bound by any particular theory, theInventors believe that the alkaline environment facilitates dissolutionof the outer layer and thereby also disintegration of the outer layersince the pH of the alkaline environment is above the pH threshold ofthe second polymeric material, thereby accelerating release of the drugfrom the formulation.

In principle, any pharmacologically acceptable base may be used. Thebase is typically a non-polymeric compound. Suitable bases includeinorganic bases such as sodium hydroxide, potassium hydroxide andammonium hydroxide, and organic bases such as triethanolamine, sodiumbicarbonate, potassium carbonate, trisodium phosphate, trisodium citrateor physiologically tolerated amines such as triethylamine. Hydroxidebases in general, and sodium hydroxide in particular, are preferred.

In embodiments in which the third polymeric material is a fullyneutralised polycarboxylic acid polymer, the base entrapped within theinner layer is usually the base that was used to neutralise the polymerand to adjust the pH of the inner coating preparation to a pH from aboutpH 5.5 to about pH 10, e.g. about pH 7.5 to about pH 10 (see below).

In embodiments in which the third polymeric material is a non-ionicpolymer, the inner layer usually comprises either a base, or moretypically a combination of a base and a buffer agent.

The amount of base present in the inner layer would depend at least inpart on the final pH of the inner coating preparation prior to coating agiven batch of cores; the number of cores to be coated in the batch; theamount of the inner coating preparation used in the coating process ofthe batch; and the efficiency of the coating process in terms of theamount of wasted coating preparation.

Buffer Agent

The inner coating preferably comprises at least one buffer agent. Thepurpose of the buffer agent is to provide or increase pH/buffer capacityon the underside of the outer layer once intestinal fluid begins topenetrate the outer layer. Without wishing to be bound by any particulartheory, the Inventors believe that the buffer agent increases the buffercapacity in the dissolving inner layer and assists the ionisation anddissolution of the polymer(s) in the outer layer. It is believed that,for a given pH, the higher the buffer capacity, the faster the rate ofpolymer dissolution. In embodiments where there is a base in the innerlayer, the buffer agent helps maintains the alkaline environment underthe outer layer once intestinal fluid penetrates the outer layer.

The buffer agent may be an organic acid such as a pharmacologicallyacceptable non-polymeric carboxylic acid, e.g. a carboxylic acid havingfrom 1 to 16, preferably 1 to 3, carbon atoms. Suitable carboxylic acidsare disclosed in WO2008/135090A. Citric acid is an example of such acarboxylic acid. The carboxylic acids may be used in carboxylate saltform, and mixtures of carboxylic acids, carboxylate salts or both mayalso be used.

The buffer agent may also be an inorganic salt such as an alkali metalsalt, an alkali earth metal salt, an ammonium salt, and a soluble metalsalt. As metals for the soluble metal salts, manganese, iron, copper,zinc and molybdenum can be mentioned. Further preferred, the inorganicsalt is selected from chloride, fluoride, bromide, iodide, phosphate,nitrate, nitrite, sulphate and borate. Phosphates such as potassiumdihydrogen phosphate are preferred over other inorganic buffer salts andorganic acid buffers due to their greater buffer capacity at the pH ofthe coating solution, for example pH 8.

The buffer agent(s) is usually present in the inner layer in an amountfrom about 0.1 wt % to about 50 wt %. In embodiments in which thesoluble (or third) polymeric material is an at least partiallyneutralised polycarboxylic acid, the buffer agent(s) is usually presentin the inner layer in an amount from about 0.1 to about 20 wt %, e.g.from about 0.1 to about 4 wt %, preferably from about 0.1 to about 3 wt%, and more preferably about 1 wt %, based on the dry weight of thethird polymeric material. In embodiments in which the soluble (or third)polymeric material is a non-ionic polymer, the buffer agent(s) isusually present in an amount from about 10 wt % to 30 wt %, based on thedry weight of the third polymeric material.

Inner Layer

In addition to the buffer agent and/or the base, the inner layer maycomprise conventional excipients for polymer films, including thoseexcipients selected from plasticizers (such a triethyl citrate),anti-tack agents (such as GMS), and surfactants (such as polysorbate80).

The thickness of the inner coating of the core is typically from about10 μm to about 150 μm. The inner layer typically has a polymer coatingamount from about 2 mg/cm² to about 10 mg/cm², preferably from about 2mg/cm² to about 8 mg/cm², and most preferably from about 3 mg/cm² toabout 7 mg/cm², based on the dry weight of the third polymeric material,particularly for cores having a diameter from about 0.2 mm to about 30mm.

Optional Additional Layers

The formulation of the present invention may have a top coating layercoating the outer layer. The formulation may also comprise anintermediate layer between the outer and inner layers, provided that theintermediate layer does not affect adversely the release characteristicsof the formulation. However, the outer layer is usually provided incontact with the inner layer, that is to say the outer layer is usuallyapplied directly on to the inner layer, i.e. there is usually nointermediate layer separating the inner and outer layers.

The Core

The “core” is the solid body on which the inner layer is applied. Thecore may be any suitable dosage form, for example, a tablet, a pellet, agranule, a microparticle, a hard or soft capsule, or a microcapsule. Inpreferred embodiments, the core is a tablet or a capsule.

The invention has application in embodiments in which the core iscompatible with the inner layer which is typically alkaline, or providesan alkaline environment on exposure to moisture. Such embodiments arelikely to include cases where the core is neutral, or is at neutral pH.However, the invention has particular application in embodiments inwhich the core or components within the core are incompatible with theinner layer. Such embodiments are likely to include cases where the coreis acidic, or is at an acidic pH. Such an acidic core would not becompatible with an alkaline inner layer and the isolation layer wouldhave the added benefit of preventing unwanted interaction between thecore and the inner layer.

The core comprises the drug(s). The drug(s) may be contained within thebody of the core, for example within the matrix of a tablet or pellet,or within the contents encapsulated within a capsule. Alternatively, thedrug may be in a coating applied to the core, for example where the coreis a bead of edible material such as sugar, e.g. where the core is inthe form of a nonpareil bead or dragée. The core may be “acidic” becausethe drug or any component within the core comprises at least one acidicgroup.

The core may consist of the drug(s) alone, or more usually may consistof the drug(s) and at least one pharmacologically acceptable excipient.In this connection, the core is typically a tablet or pellet andconsists of a mixture of the drug(s) with a filler or diluent material,e.g. lactose or cellulose material such as microcrystalline cellulose; abinder, e.g. polyvinylpyrrolidone (“PVP”) or hydroxypropylmethylcellulose (HPMC); a disintegrant, e.g. croscarmellose sodium (e.g.Ac-Di-Sol™) and sodium starch glycolate (e.g. Explotab™); and/or alubricant, e.g. magnesium stearate and talc. The core may be acompressed granulate comprising at least some of these materials.

The minimum diameter of each core is typically at least about 10⁻⁴ m,usually at least about 5×10⁻⁴ m and, preferably, at least about 10⁻³ m.The maximum diameter is usually no more than 30 mm, typically no morethan 25 mm and, preferably, no more than 20 mm. In preferredembodiments, the core has a diameter from about 0.2 mm to about 25 mm,and preferably from about 0.2 mm to about 4 mm (e.g. for pellets ormini-tablets) or from about 15 mm to about 25 mm (e.g. for certaintablets or capsules). The term “diameter” refers to the largest lineardimension through the core.

The formulation may comprise a plurality of coated cores in order toprovide a single dose of the drug(s), particularly in embodiments inwhich the core is “small”, e.g. having a diameter of less than 5 mm.Multiunit dosage forms comprising coated cores having a diameter of lessthan 3 mm may be preferred.

The present invention has application in a multi-phasic drug releaseformulation comprising at least two pluralities of coated cores, e.g.coated pellets, in the same dosage form, e.g. a capsule, in which thecoated cores of one plurality are differentiated from the coated coresof the or each other plurality by the coating. The coatings may differfrom one plurality to the next in terms of coating thickness orcomposition, e.g. the ratio and/or identity of components. Multi-phasicdrug release formulations would be particularly suitable for suffers ofCrohn's disease affecting different regions along the intestine.

Release from formulations according to the present invention istypically delayed until the proximal small intestine, usually at leastthe distal ileum and, preferably, the colon. Release from certainformulations may also be sustained. However, in preferred formulations,release is pulsatile.

The time between initial exposure to conditions suitable for drugrelease and the start of drug release is known as the “lag time”. Thelag time depends on a number of factors including coating thickness andcomposition and may vary from one patient to the next. Formulationsaccording to the present invention usually display a lag time in colonicconditions of at least 10 minutes. In most embodiments, the lag time isfrom about 10 minutes to about 8 hours. For example, the lag time infaecal slurry at pH 6.8 may be from about 10 minutes to about 2 hours,e.g. from about 30 minutes to about 1.5 hours. Complete release of thedrug may be achieved in no more than 5 hours, e.g. no more than 4 hours,after exposure to these conditions.

A formulation is usually defined as gastric resistant if there is lessthan 10 wt % drug release in acidic media after 2 hours. Formulationsaccording to the present invention typically display far less than 10 wt% drug release in acidic media and may be considered to be gastricresistant. The formulations usually display less than 1 wt % drugrelease in acidic media and, typically, display substantially no drugrelease in acidic media. When starch is combined with an acrylate filmforming material to form the outer layer of the coating for the core,typically less than 5% drug release occurs over 5 hours in conditionssimulating the stomach and small intestine.

In one embodiment, the core is a tablet having a diameter of 15-25 mm.The outer layer preferably comprises a 30:70 mixture of high amylosestarch, e.g. Eurylon™ VII or VI, and a polymethacrylate polymer, e.g.Eudragit™ S, and the inner layer preferably comprises a fullyneutralized polymethacrylate polymer, e.g. Eudragit™ S, applied from aninner coating preparation having a pH of about 8. The core is preferablycoated with the inner layer to a thickness from about 3 to about 7mg/cm² (based on dry weight of the polymethacrylate polymer) to form aninner layer coated core, which is then coated with the outer layer to athickness from about 4 to about 8 mg/cm² (based on dry weight ofpolymethacrylate polymer).

Different Aspects

Release of a drug in the colon may be considered to be a medical methodunder a broad definition of the term. However, in the absence oftreatment of a particular indication, acceleration of initial drugrelease in the colon may be viewed as a non-medical technical effect.Accordingly, there is provided, by way of a second aspect of the presentinvention, a non-medical use of an isolation layer to accelerate drugrelease in the intestine of a subject from a delayed release drugformulation for oral administration to said subject, said formulationcomprising:

-   -   a core comprising said drug;    -   said isolation layer coating said core; and    -   an outer coating for providing intestinal release of said drug,        said outer coating comprising an outer layer and an inner layer,

wherein the outer layer comprises a pH dependently soluble polymericmaterial which has a pH threshold at about pH 5 or above, and

wherein the inner layer comprises a soluble polymeric material which issoluble in intestinal fluid or gastrointestinal fluid, said solublepolymeric material being selected from the group consisting of apolycarboxylic acid polymer that is at least partially neutralised, anda non-ionic polymer, provided that, where said soluble polymericmaterial is a non-ionic polymer, said inner layer comprises at least oneadditive selected from a buffer agent and a base.

According to a third aspect of the present invention, there is provideda method of accelerating drug release in the colon of a subject from adelayed release drug formulation for oral administration to saidsubject, said formulation comprising:

-   -   a core comprising said drug; and    -   an outer coating for providing intestinal release of said drug,        said outer coating comprising an outer layer and an inner layer,

wherein the outer layer comprises a pH dependently soluble polymericmaterial which has a pH threshold at about pH 5 or above, and

wherein the inner layer comprises a soluble polymeric material which issoluble in intestinal fluid or gastrointestinal fluid, said solublepolymeric material being selected from the group consisting of apolycarboxylic acid polymer that is at least partially neutralised, anda non-ionic polymer, provided that, where said soluble polymericmaterial is a non-ionic polymer, said inner layer comprises at least oneadditive selected from a buffer agent and a base,

said method comprising providing an isolation layer between said coreand said outer coating.

According to a fourth aspect of the present invention, there is provideda method of producing a delayed release drug formulation for oraladministration, wherein said formulation provides accelerated release ofa drug in the intestine of a subject, said method comprising:

-   -   providing a core comprising said drug;    -   coating said core with an isolation layer to produce an        isolation layer coated core; and    -   coating said isolation layer coated core with an outer coating        for providing intestinal release of said drug, said outer        coating comprising an outer layer and an inner layer,

wherein the outer layer comprises a pH dependently soluble polymericmaterial which has a pH threshold at about pH 5 or above, and

wherein the inner layer comprises a soluble polymeric material which issoluble in intestinal fluid or gastrointestinal fluid, said solublepolymeric material being selected from the group consisting of apolycarboxylic acid polymer that is at least partially neutralised, anda non-ionic polymer, provided that, where said soluble polymericmaterial is a non-ionic polymer, said inner layer comprises at least oneadditive selected from a buffer agent and a base,

The Inventors have developed some new formulations that are notdisclosed in the art and which demonstrate unexpected acceleration ofinitial drug release after exposure to the typical pH conditions of thecolon. The formulations in question use the pH dependently soluble (orsecond) polymeric material as the sole film-forming material in theouter layer. Thus, according to a fifth aspect of the present invention,there is provided a delayed release drug formulation for oraladministration to deliver a drug to the intestine of a subject, saidformulation comprising:

-   -   a core comprising said drug;    -   said isolation layer coating said core; and    -   an outer coating for providing intestinal release of said drug,        said outer coating comprising an outer layer and an inner layer,

wherein the outer layer comprises a film-forming polymeric materialconsisting of a pH dependently soluble polymeric material which has a pHthreshold at about pH 5 or above,

wherein the inner layer comprises a soluble polymeric material which issoluble in intestinal fluid or gastrointestinal fluid, said solublepolymeric material being selected from the group consisting of apolycarboxylic acid polymer that is at least partially neutralised, anda non-ionic polymer, provided that, where said soluble polymericmaterial is a non-ionic polymer, said inner layer comprises at least oneadditive selected from a buffer agent and a base. Release of the drug inthe colon from these formulations is typically accelerated as describedabove.

In addition, according to a sixth aspect of the present invention, thereis provided a delayed release drug formulation for oral administrationto deliver a drug to the intestine of a subject, said formulationcomprising:

-   -   a core comprising said drug;    -   said isolation layer coating said core; and    -   an outer coating for providing intestinal release of said drug,        said outer coating comprising an outer layer and an inner layer,

wherein the outer layer comprises a pH dependently soluble polymericmaterial which has a pH threshold at about pH 5 or above,

wherein the inner layer comprises a soluble polymeric material which issoluble in intestinal fluid or gastrointestinal fluid, said solublepolymeric material being selected from the group consisting of apolycarboxylic acid polymer that is at least partially neutralised, anda non-ionic polymer, provided that, where said soluble polymericmaterial is a non-ionic polymer, said inner layer comprises at least oneadditive selected from a buffer agent and a base, and

wherein release of said drug in the intestine is accelerated.

As described above, the Inventors have discovered that the use of anisolation layer also improves the stability of the formulation duringstorage. In this regard, according to a seventh aspect of the presentinvention, there is provided use of an isolation layer to preventdeceleration of drug release in the intestine of a subject from adelayed release drug formulation for oral administration to said subjectafter storage, said formulation comprising:

-   -   a core comprising said drug;    -   said isolation layer coating said core; and    -   an outer coating for providing intestinal release of said drug,        said outer coating comprising an outer layer and an inner layer,

wherein the outer layer comprises a pH dependently soluble polymericmaterial which has a pH threshold at about pH 5 or above, and

wherein the inner layer comprises a soluble polymeric material which issoluble in intestinal fluid or gastrointestinal fluid, said solublepolymeric material being selected from the group consisting of apolycarboxylic acid polymer that is at least partially neutralised, anda non-ionic polymer, provided that, where said soluble polymericmaterial is a non-ionic polymer, said inner layer comprises at least oneadditive selected from a buffer agent and a base.

For colonic release formulations, lag time (T_(lag)) in vitro in Krebsbuffer at pH 7.4 after 2 h at 0.1M HCl is typically increased afterstorage by no more than 5%. In absolute terms, lag time (T_(lag)) invitro in Krebs buffer at pH 7.4 after 2 h at 0.1M HCl is typicallyincreased after storage by no more than 10 minutes and preferably by nomore than 5 minutes.

The effect typically results after storage in closed high densitypolyethylene (HDPE) containers for at least 1 month at 40° C./75% RHand/or after storage in closed HDPE containers for at least 3 months at25° C./60% RH, and is particularly significant when the isolation layercomprises HPMC. Additionally or alternatively, the outer layerpreferably comprises the pH dependently soluble polymeric material inadmixture with a digestible polymeric material susceptible to attack bycolonic bacteria.

In the second to seventh aspects of the present invention, theformulation may be as defined in any of the embodiments defined inrespect of the first aspect.

According to a further aspect of the present invention, there isprovided a formulation according any previous aspect for use in a methodof medical treatment of the human or animal body by therapy.

The core comprises at least one drug. The formulation is usually used toadminister a single drug as the sole therapeutically active component.However, more than one drug may be administered in a single formulation.

The formulation of the present invention is designed to administer awide range of drugs.

Suitable drugs include those drugs which are known for intestinaladministration using known delayed release oral formulations. Thepresent invention may be used to administer drugs having a local or asystemic effect.

The formulation of the present invention has particular application inthe intestinal administration of a drug comprising at least one acidicgroup such as a carboxylic acid group. Such drugs may be acidic drugs orzwitterionic drugs. An example of such a drug is 5-aminosalicylic acid(5ASA or mesalazine).

The identity of the drug(s) in the formulation obviously depends on thecondition to be treated. In this connection, the formulation hasparticular application in the treatment of IBD (including Crohn'sdisease and ulcerative colitis); IBS; constipation; diarrhoea;infection; and carcinoma, particularly colon or colorectal cancer.

For the treatment or prevention of IBD, the formulation may comprise atleast one drug selected from the group consisting of anti-inflammatoryagents (e.g. 5ASA (otherwise known as mesalazine or mesalamine), 4ASA,sulphasalazine and balsalazide); non-steroidal anti-inflammatory agents(e.g. ibuprofen and diclofenac); steroids (e.g. prednisolone; budesonideor fluticasone); immunosuppressants (e.g. azathioprine; cyclosporin; andmethotrexate); antibiotics; and biological agents including peptides,proteins and antibody fragments. Suitable examples of biological agentsinclude alkaline phosphatase and anti-TNF antibodies such as infliximab,adalimumab, certulizumab pegol, golimumab and ustekinumab.

For the treatment or prevention of cancer, the formulation may compriseat least one antineoplastic agent. Suitable antineoplastic agentsinclude fluorouracil; methotrexate; dactinomycin; bleomycin; etoposide;taxol; vincristine; doxorubicin; cisplatin; daunorubicin; VP-16;raltitrexed; oxaliplatin; and pharmacologically acceptable derivativesand salts thereof. For the prevention of colon cancer or colorectalcancer, primarily in patients suffering from colitis, the formulationmay comprise the anti-inflammatory agent, 5ASA.

For the treatment or prevention of IBS, constipation, diarrhoea orinfection, the formulation may comprise at least one active agentsuitable for the treatment or prevention of these conditions.

Pharmacologically acceptable derivatives and/or salts of the drugs mayalso be used in the formulation. An example of a suitable salt ofprednisolone is methyl prednisolone sodium succinate. A further exampleis fluticasone propionate.

The present invention has particular application in either the treatmentof IBD (particularly, ulcerative colitis) or the prevention of coloncancer or colorectal cancer (primarily in colitis patients), both using5ASA. It also has application as a portal of entry of drugs into thesystemic circulation via the colon. This is particularly advantageousfor peptide and protein drugs which are unstable in the uppergastrointestinal tract. The present invention may also be utilised forthe purpose of chronotherapy.

In another aspect of the invention, there is provided a method oftargeting a drug to the colon comprising administering to a patient aformulation as defined above.

In a yet further aspect of the invention, there is provided the use of aformulation as defined above in the manufacture of a medicament for thetreatment or prevention of IBD (particularly ulcerative colitis); IBS;constipation; diarrhoea; infection; and cancer.

There is also provided the use of at least one drug selected fromanti-inflammatory agents and steroids in the manufacture of a medicamentcomprising a formulation as defined above for use in the treatment ofIBD. In addition, there is also provided the use of at least oneantineoplastic agent in the manufacture of a medicament comprising aformulation as defined above for use in the treatment of carcinoma.Further, there is also provided use of 5ASA in the manufacture of amedicament comprising a formulation as defined above for use in theprevention of colon cancer or colorectal cancer.

According to a still further aspect of the present invention, there isprovided a method of medical treatment or prevention of IBD or carcinomacomprises administering to a patient a therapeutic amount of aformulation as defined above.

The formulation will typically comprise a therapeutically effectiveamount of the or each drug which may be from about 0.01 wt % to about 99wt %, based on the total weight of the formulation. The actual dosagewould be determined by the skilled person using his common generalknowledge. However, by way of example, “low” dose formulations typicallycomprise no more than about 20 wt % of the drug, and preferably comprisefrom about 1 wt % to about 10 wt %, e.g. about 5 wt %, of the drug.“High” dose formulations typically comprise at least 40 wt % of thedrug, and preferably from about 45 wt % to about 85 wt %, e.g. about 50wt % or about 80 wt %.

Method

In preferred embodiments, the method of producing a delayed release drugformulation for oral administration to deliver a drug to the colontypically comprises:

-   -   forming a core comprising a drug;    -   coating the core with an isolation layer to form an isolated        core;    -   coating the isolated core using an inner coating preparation        comprising the soluble (or third) polymeric material as defined        above, in a solvent system to form an inner coated core;    -   coating the inner coated core with an outer coating preparation        comprising a pH dependently soluble (or second) polymeric        material which has a pH threshold of about pH 5 or above in a        solvent system, to form an outer coated core,

wherein, where the soluble (or third) polymeric material is a non-ionicpolymer, the inner coating preparation comprises at least one additiveselected from the group consisting of a buffer agent and a base.

The outer coating layer preparation preferably includes a digestible (orfirst) polymeric material and the solvent system of the inner coatingpreparation is preferably aqueous.

In embodiments where the third polymeric material is an at leastpartially neutralised polycarboxylic acid polymer, said method typicallycomprises dispersing a polycarboxylic acid polymer in a solvent,optionally with a buffer agent, and adding base to at least partiallyneutralise the polycarboxylic acid polymer to form the inner coatingpreparation. In preferred embodiments, the amount of base added is atleast sufficient to fully neutralise the polycarboxylic acid polymer.

In embodiments where the third polymeric material is a non-ionicpolymer, the pH of the inner coating preparation is preferably adjustedprior to coating to be at least 0.5 pH units higher than the pHthreshold of the second polymeric material.

The pH of the inner coating preparation is preferably adjusted to befrom about pH 5.5 to about pH 10, e.g. from about pH 7.5 to about pH8.5, preferably from about pH 7.8 to about pH 8.2, and more preferablyabout pH 8.

The outer coating may be applied using the method described inWO2007/122374A.

EXAMPLES

Preferred embodiments of the present invention will now be describedwith reference to the drawings, in which:—

FIG. 1 is a graph comparing drug release in 0.1N HCl (2 hours) followedby Krebs buffer pH 7.4 as a function of time, from 400 mg 5ASA tablets,coated with (a) an isolation layer of HPMC, an inner layer ofneutralized Eudragit S and an outer layer of Eudragit® S (Example 1),(b) coated with an inner layer of neutralized Eudragit S and an outerlayer of Eudragit® S (Comparative Example 1) and (c) coated with asingle layer of Eudragit S (Comparative Example 2);

FIG. 2 is a graph comparing drug release in 0.1N HCl (2 h) followed byKrebs buffer pH 7.4 as a function of time from 400 mg 5ASA tabletscoated with an isolation layer of HPMC, an inner layer of neutralizedEudragit® S and an outer layer of Eudragit® S (Example 1) after storageat 40° C./75% RH for (a) 0 days, (b) 15 days and (c) 45 days;

FIG. 3 is a graph comparing drug release in 0.1N HCl (2 h) followed byKrebs buffer pH 7.4 as a function of time from 400 mg 5ASA tabletscoated with an inner layer of neutralized Eudragit® S and an outer layerof Eudragit® S (Comparative Example 1) after storage at 40° C./75% RHfor (a) 0 days, (b) 15 days and (c) 45 days;

FIG. 4 is a graph comparing drug release in 0.1N HCl (2 h) followed byKrebs buffer pH 7.4 as a function of time from 800 mg 5ASA tabletscoated with (a) an isolation layer of HPMC, an inner layer ofneutralized Eudragit® S and an outer layer of 30:70 mixture ofstarch:Eudragit® S (Example 2), (b) an isolation layer of PVA (OpadryAMB), an inner layer of neutralized Eudragit® S and an outer layer of30:70 mixture of starch:Eudragit® S (Example 3), (c) an inner layer ofneutralized Eudragit® S and an outer layer of 30:70 mixture ofstarch:Eudragit® S (Comparative Example 3), (d) an isolation layer ofHPMC and an outer layer of 30:70 mixture of starch:Eudragit® S(Comparative Example 4), (e) an outer layer of 30:70 mixture ofstarch:Eudragit® S (Comparative Example 5);

FIG. 5 is a graph comparing drug release in 0.1N HCl (2 h) followed byKrebs buffer pH 7.4 as a function of time from 1200 mg 5ASA tabletscoated with an isolation layer of HPMC, an inner layer of neutralizedEudragit® S and an outer layer of 30:70 mixture of starch:Eudragit® S,wherein the isolation layer has a thickness of (a) 1 mg/cm² (ComparativeExample 6) (b) 3 mg/cm² (Example 4), or (c) 5 mg/cm² (ComparativeExample 7);

FIG. 6 is a graph comparing drug release in 0.1N HCl (2 h) followed byKrebs buffer pH 7.4 as a function of time from 800 mg 5ASA tabletscoated with an inner layer of neutralized Eudragit® S and an outer layerof 30:70 mixture of starch:Eudragit® S (Comparative Example 3) beforestorage (Initial) and after storage in a closed HDPE bottle at 40°C./75% RH for 1 month and 3 months;

FIG. 7 is a graph comparing drug release in 0.1N HCl (2 h) followed byKrebs buffer pH 7.4 as a function of time from 800 mg 5ASA tabletscoated with an isolation layer of HPMC, an inner layer of neutralizedEudragit® S and an outer layer of 30:70 mixture of starch:Eudragit® S(Example 2) before storage (Initial) and after storage in a closed HDPEbottle at 40° C./75% RH for 1 month and 3 months;

FIG. 8 is a graph comparing drug release in 0.1N HCl (2 h) followed byKrebs buffer pH 7.4 as a function of time from 800 mg 5ASA tabletscoated with an isolation layer of HPMC, an inner layer of neutralizedEudragit® S and an outer layer of 50:50 mixture of starch:Eudragit® S(Example 5) before storage (Initial) and after storage in a closed HDPEbottle at 40° C./75% RH for 1 month and 3 months;

FIG. 9 is a graph depicting drug release in 0.1N HCl (2 h) followed byKrebs buffer pH 7.4 as a function of time from 800 mg 5ASA tabletscoated with an inner layer of neutralized Eudragit® S and an outer layerof 30:70 mixture of starch:Eudragit® S (Comparative Example 3) beforestorage (Initial) and after storage in an open HDPE bottle at 25° C./60%RH for 1 month and for 3 months;

FIG. 10 is a graph depicting drug release in 0.1N HCl (2 h) followed byKrebs buffer pH 7.4 as a function of time from 800 mg 5ASA tabletscoated with an isolation layer of HPMC, an inner layer of neutralizedEudragit® S and an outer layer of 30:70 mixture of starch:Eudragit® S(Example 2) before storage (Initial) and after storage in an open HDPEbottle at 25° C./60% RH for 1 month and 3 months;

FIG. 11 is a graph comparing drug release in 0.1N HCl (2 h) followed byKrebs buffer pH 7.4 as a function of time from 800 mg 5ASA tabletscoated with an isolation layer of HPMC, an inner layer of neutralizedEudragit® S and an outer layer of 50:50 mixture of starch:Eudragit® S(Example 5) before storage (Initial) and after storage in an open HDPEbottle at 25° C./60% RH for 1 month and 3 months.

MATERIALS

5-aminosalicylic acid (mesalazine EP) was purchased from CambrexKarlskoga AB, Karlskoga, Sweden. Lactose (Tablettose 80) was purchasedfrom Meggle, Hamburg, Germany. Sodium starch glycolate (Explotab™) waspurchased from JRS Pharma, Rosenberg, Germany. Talc was purchased fromLuzenac Deutschland GmbH, Düsseldorf, Germany. Polyvinylpyrrolidone(PVP) was purchased from ISP Global Technologies, Köln, Germany.Magnesium stearate was purchased from Peter Greven GmbH, BadMünstereifel, Germany. Eudragit® S 100, Eudragit® L 30 D-55 andEudragit® FS 30 D were all purchased from Evonik GmbH, Darmstadt,Germany. Maize starch (NI-460 and Eurylon VI or 6) was purchased fromRoquette, Lestrem, France. Polysorbate 80, butan-1-ol and sodiumhydroxide were all purchased from Sigma-Aldrich, Buchs, Switzerland.Potassium dihydrogen phosphate, glyceryl monostearate (GMS), triethylcitrate (TEC) and ammonia solution (25%) were all purchased from VWRInternational LTD, Poole, UK.

Preparation of 400 mg 5ASA Tablet Cores

Oblong shaped 400 mg 5ASA tablet cores with dimensions 14.5×5.7 mm wereprepared by fluid bed granulation followed by blending and compression.Each tablet contained 76.9 wt % 5ASA (400 mg; drug); 14.7 wt % lactose(filler); 1.7 wt % PVP (binder); 3.5 wt % sodium starch glycolate(disintegrant); and 2 wt % talc and 1.2 wt % magnesium stearate(lubricants).

The obtained tablet cores were coated as discussed below in Examples 1 &2 and in Comparative Examples 1 to 5.

Preparation of 800 mg 5ASA Tablet Cores

Oblong shaped 800 mg tablets with dimensions 8×17 mm were prepared bygranulation followed by blending and compression. Each tablet contained800 mg 5ASA (drug) and additional excipients, including lactose(filler); PVP (binder); sodium starch glycolate (disintegrant); and talcand magnesium stearate (lubricants).

The obtained tablet cores were coated as discussed below in Examples 8to 11 and in Comparative Examples 7 to 11.

Preparation of 1200 mg 5ASA Tablet Cores

Oblong-shaped 1200 mg 5ASA tablet cores (having dimensions 21×10 mm)were prepared by wet granulation. Each tablet contained 85.7 wt % 5ASA(1200 mg), 9.2 wt % microcrystalline cellulose, 1.7 wt % HPMC, 2.9 wt %sodium starch glycolate, and 0.5 wt % magnesium stearate.

The obtained tablet cores were coated as discussed below in Examples 3to 7 and in Comparative Example 6.

Example 1 400 mg 5ASA Tablets with Isolation Layer of HPMC/Inner Layerof Neutralised Eudragit® S/Outer Layer of Eudragit® S

Isolation Layer

The isolation layer was formed from a mixture of HPMC and 10% triethylcitrate (TEC), based on dry polymer weight.

The HPMC was dissolved in water under magnetic stirring and then TEC wasadded to form a coating preparation. The coating preparation was sprayedonto 400 mg 5ASA cores using a fluid bed spray coating machine toachieve a coating amount of 3 mg polymer/cm².

The coating parameters were as follows: spray rate 3.1 g/min/kg tabletcores, atomizing pressure 0.2 bar, and inlet air temperature 40° C.

Inner Layer

The inner layer was applied to the isolation layer coated tablets froman aqueous preparation of Eudragit® S 100, where the pH was adjusted topH 8. The composition of the inner layer also included 50% of triethylcitrate (based on dry polymer weight), 10% potassium dihydrogenphosphate (based on dry polymer weight), 10% glyceryl monostearate(based on dry polymer weight) and 40% polysorbate 80 (based on GMSweight). The pH was adjusted using 1M NaOH until the pH 8 was obtained.

Potassium dihydrogen phosphate and triethyl citrate were dissolved indistilled water, after which a dispersion of Eudragit® S 100 was addedunder mechanical agitation. The pH was then adjusted to pH 8 with 1MNaOH and the solution was left mixing for 1 hour.

A GMS emulsion was prepared at a concentration of 10% w/w. Polysorbate80 (40% based on GMS weight) was dissolved in distilled water followedby dispersion of GMS. This preparation was then heated to 75° C. for 15minutes under strong magnetic stirring in order to form the emulsion.The emulsion was cooled to room temperature under stirring.

The GMS emulsion was added to the neutralised Eudragit® S solution toform an inner layer coating preparation which was coated onto theisolation layer coated tablets using a fluid bed spray coating machineuntil the coating amount reached 5 mg polymer/cm² to form inner layercoated tablets.

The coating parameters were as follows: spraying rate 20 ml/min/kgtablets, atomizing pressure 0.2 bar and inlet air temperature 40° C.

Outer Layer

The outer coating layer was applied from an organic solution ofEudragit® S 100. The coating solution contains 20% triethyl citrate(based on dry polymer weight), 10% glyceryl monostearate (based on drypolymer weight) and 40% polysorbate 80 (based on GMS weight).

Triethyl citrate was dissolved in 96% ethanol followed by Eudragit® S100 under mechanical stirring and mixing was continued for 1 hour.

A GMS emulsion was prepared at a concentration of 10% w/w. Polysorbate80 (40% based on GMS weight) was dissolved in distilled water followedby dispersion of the GMS. This dispersion was then heated to 75° C. for15 minutes under strong magnetic stirring in order to form the emulsion.The emulsion was cooled to room temperature under stirring.

The GMS preparation was added to the Eudragit® S 100 solution and thefinal coating solution was coated on to the inner layer coated tabletsusing a fluid bed spray coating machine to achieve a coating amount of 5mg Eudragit® S polymer/cm².

The coating parameters were as follows: spraying rate 16 ml/min/kgtablets, atomizing pressure 0.2 bar and inlet air temperature 40° C.

Example 2 800 mg 5ASA Tablets with Isolation Layer of HPMC/Inner Layerof Neutralised Eudragit® S/Outer Layer of 30:70 Mixture ofStarch:Eudragit® S

Isolation Layer

The isolation layer was formed from a mixture of HPMC and 20% PEG 6000(based on dry polymer weight).

The polymer was dissolved in water under magnetic stirring and then thePEG 6000 was added. The final preparation was sprayed onto 800 mg 5ASAcores using a perforated pan coater to achieve a coating amount of 3 mgpolymer/cm² to form isolation layer coated tablets. The coatingparameters were as follows: spray rate 2.4 g/min/kg tablet cores,atomizing pressure 0.7 bar, and inlet air volume 15 m³/h/Kg tablets andproduct temperature 34° C.

Inner Layer

The inner layer was applied using an aqueous preparation of Eudragit® S100, where the pH was adjusted to pH 8. The composition of the middlelayer also includes 70% triethyl citrate (based on dry polymer weight),1% potassium dihydrogen phosphate (based on dry polymer weight), 10%glyceryl monostearate (based on dry polymer weight) and 40% polysorbate80 (based on GMS weight). The pH was adjusted using 1M NaOH until the pH8 is obtained.

Potassium dihydrogen phosphate and triethyl citrate were dissolved indistilled water, followed by dispersion of the Eudragit® S 100 undermechanical agitation. The pH was then adjusted to pH 8 with 1M NaOH andleft mixing for 1 h.

A GMS emulsion was prepared at a concentration of 10% w/w. Polysorbate80 (40% based on GMS weight) was dissolved in distilled water followedby dispersion of GMS. This preparation was then heated to 75° C. for 15minutes under strong magnetic stirring in order to form an emulsion. Theemulsion was cooled to room temperature under stirring.

The GMS emulsion was added to the neutralised Eudragit® S solution andthe final preparation was coated onto isolation layer coated tabletsusing a perforated pan coater until the coating amount reached 5 mgpolymer/cm² to produce inner layer coated tablets. The total solidscontent of the coating solution was 10%. The coating parameters were asfollows: spraying rate 3.1 g/min/kg tablets, atomizing pressure 0.6 bar,inlet air volume 15 m3/h/Kg tablets and product temperature 26.5° C.

Outer Layer

The outer layer was applied using a mixture of an aqueous starchdispersion and an organic Eudragit® S 100 solution. The aqueous starchdispersion was prepared by dispersing maize starch into butan-1-ol,followed by water, under magnetic stirring. The ratio of maizestarch:butan-1-ol:water was 1:2:22. The resulting dispersion was heatedto boiling and then cooled under stirring overnight. The organicEudragit® S 100 solution was prepared by dissolving Eudragit® S 100 in96% ethanol under high speed stirring. The final solution containedabout 6% polymer solids.

The starch dispersion was added dropwise to the Eudragit® S 100 solutionto obtain a ratio of starch:Eudragit® S of 30:70. The mixture was mixedfor 2 h, 20% triethyl citrate (based on total polymer weight) and 5%glyceryl monostearate (GMS, based on total polymer weight) were addedand mixing was continued for a further 2 h.

13.18% iron oxide red (based on Eudragit® polymer weight) and 2.27% ironoxide yellow (based on Eudragit® polymer weight) were suspended inethanol under high shear homogenization and this suspension was addedinto the starch and Eudragit® mixture and mixed for a further 30minutes.

The GMS was added in the form of an emulsion prepared at a concentrationof 5% w/w. Polysorbate 80 (40% based on GMS weight) was dissolved indistilled water followed by dispersion of the GMS. This dispersion wasthen heated to 75° C. for 15 minutes under strong magnetic stirring inorder to form an emulsion. The emulsion was cooled to room temperatureunder stirring.

The final preparation was coated onto the inner layer coated tabletsusing a perforated pan coater machine until a coating having 5 mgEudragit® polymer/cm² was obtained. The spray coating parameters were asfollows: spraying rate 8.0 g/min/kg tablets, atomizing pressure 0.4 bar,inlet air volume 100 m³/h/Kg tablets and product temperature 34.5° C.

Example 3 800 mg 5ASA Tablets with Isolation Layer of PVA/Inner Layer ofNeutralised Eudragit® S/Outer Layer of a 30:70 Mixture ofStarch/Eudragit® S

Isolation Layer

The isolation layer was formed using Opadry® AMB (a polyvinylalcohol-based product). The polymer was dissolved in water undermagnetic stirring and mixed for 45 minutes. The final preparation wassprayed onto 800 mg 5ASA cores using a pan-coating machine to achieve acoating amount of 3.61 mg Opadry®/cm². The coating parameters were asfollows: spray rate 7.0 g/min/kg tablet cores, atomizing pressure 0.6bar, inlet air volume 75 m³/h per kg tablet cores and producttemperature 42° C.

Inner Layer

The inner layer was prepared according to Example 2.

Outer Layer

The outer layer was prepared according to Example 2

Example 4 1200 mg 5ASA Tablets with Isolation Layer of HPMC (3mg/cm²)/Inner Layer of Neutralised Eudragit® S/Outer Layer of 30:70Mixture of Starch:Eudragit® S

Isolation Layer

The isolation layer was prepared according to Example 2. The finalpreparation was sprayed onto 1200 mg 5ASA cores using a perforatedpan-coating machine to achieve a coating amount of 3 mg polymer/cm² toform isolation layer coated tablets. The coating parameters were asfollows: spray rate 2.33 g/min. per kg tablet cores, atomizing pressure0.7 bar, inlet air volume 16.3 m³/h per kg tablet cores and producttemperature 33° C.

Inner Layer

The inner coating was prepared according to Example 2. The finalpreparation was coated on to the isolation layer coated tablets using aperforated pan coater machine until the coating amount reached 5 mgpolymer/cm². The total solids content of the coating solution isapproximately 10%.

The coating parameters were as follows: spraying rate 2.9 g/min/kgtablets, atomizing pressure 0.6 bar, and inlet air volume 16.3 m³/h/kgtablets and product temperature 33° C.

Outer Layer

The outer layer was prepared according to Example 2. The finalpreparation was coated onto inner layer coated tablets using aperforated pan coater machine until a coating having 5 mg Eudragit® Spolymer/cm² was obtained. The spray coating parameters were as follows:spraying rate 3.1 g/min/kg tablets, atomizing pressure 0.4 bar, inletair volume 21.7 m³/h/kg tablets and product temperature 34° C.

Example 5 800 mg 5ASA Tablets with Isolation Layer of HPMC/Inner Layerof Neutralised Eudragit® S/Outer Layer of a 50:50 Mixture ofStarch/Eudragit® S

Isolation Layer

The isolation layer was prepared according to Example 2.

Inner Layer

The inner layer was prepared according to Example 2

Outer Layer

The outer layer was applied from a mixture of an aqueous starchdispersion and an organic Eudragit® S 100 solution.

The aqueous starch dispersion was prepared by dispersing maize starchinto butan-1-ol, followed by water, under magnetic stirring. The ratioof maize starch:butan-1-ol:water was 1:1:9.53. The resulting dispersionwas heated to boiling and then cooled under stirring overnight. The %solids content of the cooled preparation was calculated based on thefinal weight of the dispersion (considering the evaporation duringheating).

The organic Eudragit® S 100 solution was prepared by dissolvingEudragit® S 100 in 96% ethanol under high speed stirring. The finalsolution contained about 6% polymer solids.

The starch dispersion was added dropwise to the Eudragit® S 100 solutionto obtain a ratio of starch:Eudragit® S of 50:50. The mixture was mixedfor 2 h, 20% triethyl citrate (based on total polymer weight) and 5%glyceryl monostearate (GMS, based on total polymer weight) were addedand mixing continued for a further 2 h.

13.18% iron oxide red (based on Eudragit® polymer weight) and 2.27% ironoxide yellow (based on Eudragit® polymer weight) were suspended inethanol under high shear homogenization and this suspension was addedinto the starch and Eudragit mixture and mixing continued for a further30 minutes.

The GMS was added in the form of an emulsion prepared at a concentrationof 5% w/w. Polysorbate 80 (40% based on GMS weight) was dissolved indistilled water followed by dispersion of the GMS. This dispersion wasthen heated to 75° C. for 15 minutes under strong magnetic stirring inorder to form an emulsion. The emulsion was cooled to room temperatureunder stirring. The final preparation was coated onto the inner layercoated tablets using a perforated pan coater until a coating having 5 mgEudragit® S polymer/cm² was obtained. The spray coating parameters wereas follows: spraying rate 8.0 g/min/kg tablets, atomizing pressure 0.4bar, inlet air volume 100 m³/h/kg tablets and product temperature 35.5°C.

Comparative Example 1 400 mg 5ASA Tablets with Inner Layer ofNeutralised Eudragit® S/Outer Layer of Eudragit® S

Inner Layer

The inner layer was prepared according to Example 1.

Outer Layer

The outer layer was prepared according to Example 1

Comparative Example 2 400 mg 5ASA Tablets with a Single Layer ofEudragit® S

The single layer of Eudragit S was prepared according to Example 1 andapplied directly on 400 mg 5ASA tablet cores (without isolation andwithout inner layer).

Comparative Example 3 800 mg 5ASA Tablets with Inner Layer ofNeutralised Eudragit® S/Outer Layer of a 30:70 Mixture ofStarch:Eudragit® S

Inner Layer

The inner layer was prepared according to Example 2.

Outer Layer

The outer layer was prepared according to Example 2.

Comparative Example 4 800 mg 5ASA Tablets with Isolation Layer ofHPMC/Outer Layer of a 30:70 Mixture of Starch:Eudragit® S

Isolation Layer

The isolation layer was prepared according to Example 2

Outer Layer

The outer layer was prepared according to Example 2

Comparative Example 5 800 mg 5ASA Tablets with a Single Layer of a 30:70Mixture of Starch/Eudragit® S

The single layer of a 30:70 mixture of starch/Eudragit® S was preparedaccording to Example 2, and applied directly on 800 mg 5ASA tablet cores(without isolation layer and without inner layer).

Comparative Example 6 1200 mg 5ASA Tablets with Isolation Layer of HPMC(1 mg/cm²)/Inner Layer of Neutralised Eudragit® S/Outer Layer of 30:70Mixture of starch:Eudragit® S

Isolation Layer

The isolation layer was applied from a mixture of HPMC and 20%polyethylene glycol 6000 (PEG 6000), based on dry polymer weight.

The HPMC polymer was dissolved in water under magnetic stirring and thenPEG 6000 was added. The final preparation was sprayed onto 1200 mg 5-ASAcores using a perforated pan-coating machine to achieve a coating amountof 1 mg polymer/cm² to form isolation layer coated tablets.

The coating parameters were as follows: spray rate 9.75 g/min. per kgtablet cores, atomizing pressure 0.7 bar, inlet air volume 75 m³/h/kgtablets and product temperature 32° C.

Inner Layer

The inner layer was prepared according to Example 4

Outer Layer

The outer layer was prepared according to Example 4.

Comparative Example 7 1200 mg 5ASA Tablets with Isolation Layer of HPMC(5 mg/cm²)/Inner Layer of Neutralised Eudragit® S/Outer Layer of 30:70Mixture of Starch:Eudragit® S

Isolation Layer

The isolation layer was formed from a mixture of HPMC and 20%polyethylene glycol 6000 (PEG 6000), based on dry polymer weight.

The HPMC polymer was dissolved in water under magnetic stirring and thenPEG 6000 was added. The final preparation was sprayed onto 1200 mg 5ASAcores using a pan-coating machine to achieve a coating amount of 5 mgpolymer/cm² to form isolation layer coated tablets.

Inner Layer

The inner layer was prepared according to Example 4.

Outer Layer

The outer layer was prepared according to Example 4.

The coating parameters were as follows: spray rate 5.75 g/min. per kgtablet cores, atomizing pressure 0.7 bar, inlet air volume 75 m³/h perkg tablet cores and product temperature 32° C.

Drug Release Test—Effect of pH Alone

In vitro dissolution studies were performed on a USP type II apparatususing a paddle speed of 50 rpm and a media temperature of 37±0.5° C.Tablets were first tested in 0.1 M HCl for 2 h followed by 8 h in Krebsbuffer (pH 7.4). The pH of the buffer was stabilized at 7.4±0.05 bycontinuously sparring with 5% CO₂/95% O₂. Absorbance measurements weretaken at 5 minute intervals, with an absorbance wavelength of 301 nm inHCl and 330 nm in Krebs buffer. The composition per litre of Krebsbuffer is 0.16 g of KH₂PO₄, 6.9 g of NaCl, 0.35 g KCl, 0.29 gMgSO₄.7H₂O, 0.376 g CaCl₂.2H₂O and 2.1 g NaHCO₃. Only the measurementstaken at 30 or 60 minute intervals are depicted in the figures.

Storage

Drug release was tested before storage (Initial) and after storage underdifferent conditions at the 1 month and 3 month points. The storageconditions exemplified herein are (i) open HDPE bottles at 25° C./60% RH(relative humidity); (ii) closed HDPE bottles at 25° C./60% RH; (iii)open HDPE bottle at 40° C./75% RH; and (iv) closed HDPE bottles 40°C./75% RH.

Results

The results depicted in FIG. 1 clearly indicate that initial drugrelease is quicker (i.e. T_(lag) is reduced) from 400 mg 5ASA tabletscoated with an isolation layer of HPMC, an inner layer of neutralizedEudragit S and an outer layer of Eudragit S (Example 1) than if theisolation layer is absent (Comparative Example 1) or both the isolationlayer and the inner layer are absent (Comparative Example 2).

The results depicted in FIGS. 2 to 3 indicate that the drug release issubstantially unaffected after storage (at 40° C./75% RH) after 45 daysfrom tablets coated with an HPMC isolation layer, an inner layer ofneutralized Eudragit S and outer layer of Eudragit S (Example 1) whencompared to equivalent tablets without the isolation layer (ComparativeExample 1). Clearly, the use of an HPMC isolation layer improves thestability of the tablets during storage.

The results depicted in FIG. 5 indicate that initial release drugrelease is quicker from 1200 mg 5ASA tablets coated with an isolationlayer of HPMC, an inner layer of neutralized Eudragit S and an outerlayer of a 30:70 mixture of starch:Eudragit S when the isolation layerhas a thickness of 3 mg polymer/cm² (Example 4) than if the isolationlayer has a thickness of 1 mg polymer/cm² (Comparative Example 6) or 5mg polymer/cm² (Comparative Example 7)) although it should be noted thatinitial release is accelerated in each of these cases.

Turning to FIGS. 4 to 11, the results indicate that presence of anisolation layer made of HPMC (Example 2) leads to a faster drug releasecompared to tablets coated only with an inner layer of neutralizedEudragit S and an outer layer of a 30:70 mixture of starch:Eudragit S(Comparative Example 3). Furthermore, in the absence of the middle layer(Comparative Example 4), the isolation layer contributes to a later drugrelease when compared to a single layer of 30:70 mixture ofstarch:Eudragit S (Comparative Example 5). This result demonstrates thatimproved drug release is not inevitable if an isolation layer is presentbetween the core and the alkaline inner layer.

Moreover, when using an isolation layer of PVA, the contribution to drugrelease acceleration was actually higher than the one given by the innerlayer alone (Example 3, Comparative Example 3 and Comparative Example9). In the absence of isolation layer (Comparative Example 3), after 1month storage at 40° C./75% RH, the drug release was delayed even ifstored in closed HDPE bottles. However, the presence of an HPMCisolation layer (Example 2) avoided the delay in drug release after 1month at 40° C./75% RH for the tablets stored in closed HDPE bottles.The same observations are also valid when the outer layer has a 50:50mixture of starch and Eudragit S (Example 5).

At 25° C./60% RH, even in open conditions, there is no significantchange in drug release if an isolation layer is present (Example 2 andExample 5), whereas in the absence of the isolation layer (ComparativeExample 3), tablets stored openly show a delayed release after 1 month.

It can be seen therefore that the delayed release formulation accordingto the present invention is significantly superior to comparativeformulations.

Whilst the invention has been described with reference to a preferredembodiment, it will be appreciated that various modifications arepossible within the spirit or scope of the invention as defined in thefollowing claims.

In this specification, unless expressly otherwise indicated, the word‘or’ is used in the sense of an operator that returns a true value wheneither or both of the stated conditions is met, as opposed to theoperator ‘exclusive or’ which requires that only one of the conditionsis met. The word ‘comprising’ is used in the sense of ‘including’ ratherthan in to mean ‘consisting of’. All prior teachings acknowledged aboveare hereby incorporated by reference. No acknowledgement of any priorpublished document herein should be taken to be an admission orrepresentation that the teaching thereof was common general knowledge inAustralia or elsewhere at the date hereof.

The invention claimed is:
 1. A delayed release drug formulation for oraladministration, said delayed release drug formulation comprising: a corecomprising a drug; an isolation layer coating said core; and an outercoating for providing colonic release of said drug, said outer coatingcomprising an outer layer and an inner layer, wherein said outer layercomprises a pH dependently soluble polymeric material which has a pHthreshold at about pH 6.5 or above, and wherein the inner layercomprises a soluble polymeric material which is soluble in intestinalfluid or gastrointestinal fluid, said soluble polymeric material being apolycarboxylic acid polymer that is at least partially neutralized,wherein at least 10% of the carboxylic acid groups of the polycarboxylicacid polymer are in the form of carboxylate anions.
 2. The delayedrelease drug formulation of claim 1, wherein colonic release of saiddrug from said delayed release drug formulation is accelerated comparedto an equivalent formulation without said isolation layer.
 3. Thedelayed release drug formulation of claim 1, wherein lag time in vitroin Krebs buffer at pH 7.4 after 2 h at 0.1M HCl is reduced by at least10%.
 4. The delayed release drug formulation of claim 1, wherein lagtime in vitro in Krebs buffer at pH 7.4 after 2 h at 0.1M HCl is reducedby at least 10 minutes.
 5. The delayed release drug formulation of claim1, having a coating amount from about 1 mg polymer/cm² to about 5 mgpolymer/cm².
 6. The delayed release drug formulation of claim 1, havinga thickness from about 5 μm to about 100 μm.
 7. The delayed release drugformulation of claim 1, wherein said isolation layer comprises at leastone non-ionic polymer.
 8. The delayed release drug formulation of claim1, wherein said isolation layer comprises at least one polymer selectedfrom the group consisting of methylcellulose; hydroxypropyl cellulose;hydroxypropyl methylcellulose; poly(ethylene oxide)-graft-polyvinylalcohol; polyvinylpyrollidone; and polyvinyl alcohol.
 9. The delayedrelease drug formulation of claim 1, wherein said isolation layercomprises hydroxypropyl methylcellulose.
 10. The delayed release drugformulation of claim 1, wherein said polycarboxylic acid polymer isfully neutralized.
 11. A method of accelerating drug release in theintestine of a subject from a delayed release drug formulation for oraladministration to said subject, the method comprising administering thedelayed release drug formulation comprising: an isolation layer betweena core and an outer coating, the core comprising a drug; and the outercoating being suitable for providing intestinal release of said drug,and said outer coating comprising an outer layer and an inner layer,wherein the outer layer comprises a pH dependently soluble polymericmaterial which has a pH threshold at about pH 5 or above, and whereinthe inner layer comprises a soluble polymeric material which is solublein intestinal fluid or gastrointestinal fluid, said soluble polymericmaterial being a polycarboxylic acid polymer that is at least partiallyneutralized, wherein at least 10% of the carboxylic acid groups of thepolycarboxylic acid polymer are in the form of carboxylate anions.
 12. Amethod of producing a delayed release drug formulation for oraladministration, said method comprising: providing a core comprising adrug; coating said core with an isolation layer to produce an isolatedcore; and coating said isolated core with an outer coating for providingintestinal release of said drug, said outer coating comprising an outerlayer and an inner layer, wherein said delayed release drug formulationprovides accelerated release of the drug in the intestine of thesubject; wherein the outer layer comprises a pH dependently solublepolymeric material which has a pH threshold at about pH 5 or above, andwherein the inner layer comprises a soluble polymeric material which issoluble in intestinal fluid or gastrointestinal fluid, said solublepolymeric material being a polycarboxylic acid polymer that is at leastpartially neutralized, wherein at least 10% of the carboxylic acidgroups of the polycarboxylic acid polymer are in the form of carboxylateanions.
 13. A method, of preventing deceleration of drug release in theintestine of a subject from a delayed release drug formulation for oraladministration administering the delayed release drug formulationcomprising: a core comprising a drug; an isolation layer coating saidcore; and an outer coating for providing intestinal release of saiddrug, said outer coating comprising an outer layer and an inner layer,wherein the outer layer comprises a pH dependently soluble polymericmaterial which has a pH threshold at about pH 5 or above, and whereinthe inner layer comprises a soluble polymeric material which is solublein intestinal fluid or gastrointestinal fluid, said soluble polymericmaterial being a polycarboxylic acid polymer that is at least partiallyneutralized, wherein at least 10% of the carboxylic acid groups of thepolycarboxylic acid polymer are in the form of carboxylate anions. 14.The method of claim 13, wherein lag time in vitro in Krebs buffer at pH7.4 after 2 h at 0.1M HCl is increased after storage by no more than 5%.15. The method as claimed in claim 13, wherein lag time in vitro inKrebs buffer at pH 7.4 after 2 h at 0.1M HCl is increased after storageby no more than 10 minutes.
 16. The method of claim 13, wherein saiddelayed release drug formulation is stored in a closed high densitypolyethylene container for at least 1 month at 40° C./75% RH.
 17. Themethod of claim 13, wherein said delayed release drug formulation isstored in a closed high density polyethylene container for at least 3months at 25° C./60% RH.
 18. The method of claim 13, wherein saidisolation layer comprises hydroxypropyl methylcellulose.
 19. The methodof claim 13, wherein said outer layer comprises said pH dependentlysoluble polymeric material in admixture with a digestible polymericmaterial susceptible to attack by colonic bacteria.
 20. The formulationof claim 1, wherein said core is acidic.
 21. The formulation of claim 1,wherein said drug is an anti-inflammatory agent.
 22. The formulation ofclaim 1, wherein said drug is 5-aminosalicylic acid.
 23. The formulationof claim 1, wherein said polycarboxylic acid polymer is fullyneutralized.
 24. The formulation of claim 1, wherein said pH dependentlysoluble polymeric material of said outer layer is based on the samepolycarboxylic acid polymer as said soluble polymeric material of saidinner layer, said soluble polymeric material of said inner layer havinga higher degree of neutralization than said pH dependently solublepolymeric material of said outer layer.
 25. The formulation of claim 1,wherein said polycarboxylic acid polymer of said soluble polymericmaterial of said inner layer is selected from the group consisting ofpolymethacrylate; cellulose acetate phthalate; polyvinyl acetatephthalate; hydroxypropyl methylcellulose phthalate; hydroxypropylmethylcellulose acetate succinate; cellulose acetate trimellitate;xanthan gum; alginates; and shellac.
 26. The formulation of claim 1,wherein said soluble polymeric material of said inner layer is an atleast partially neutralized co-polymer of (meth)acrylic acid and a(meth)acrylic acid C₁₋₄ alkyl ester.
 27. The formulation of claim 1,wherein said soluble polymeric material of said inner layer is a fullyneutralized co-polymer of (meth)acrylic acid and (meth)acrylic acidmethyl ester.
 28. The formulation of claim 1, wherein said inner layerfurther comprises at least one additive selected from the groupconsisting of a buffer agent and a base, wherein the buffer agent is anorganic acid or an inorganic salt.
 29. The formulation of claim 1,wherein the inner layer further comprises a buffer agent and a base,wherein the buffer agent is an organic acid or an inorganic salt. 30.The formulation of claim 1, wherein the inner layer further comprises abuffer agent and the buffer agent is selected from the group consistingof a carboxylic acid having from 1 to 16 carbon atoms, an alkali metalsalt, an alkali earth metal salt, an ammonium salt and a soluble metalsalt.
 31. The formulation of claim 1, wherein the inner layer furthercomprises a buffer agent and the buffer agent is a phosphate salt. 32.The formulation of claim 1, wherein the inner layer further comprises abuffer agent and the buffer agent is potassium dihydrogen phosphate. 33.The formulation of claim 1, wherein the inner layer further comprises abuffer agent and the buffer agent is present in the inner layer in atotal amount from about 0.1 wt % to about 50 wt % based on a dry weightof the soluble polymeric material of the inner layer.
 34. Theformulation of claim 1, wherein the inner layer further comprises abuffer agent and the buffer agent is present in the inner layer in atotal amount from about 0.1 wt % to about 20 wt % based on a dry weightof the at least partially neutralized polycarboxylic acid of the innerlayer.
 35. The formulation of claim 1, wherein the inner layer furthercomprises a buffer agent and the buffer agent is present in the innerlayer in a total amount from about 10 wt % to about 30 wt % based on adry weight of the non-ionic polymer of the inner layer.
 36. Theformulation of claim 1, wherein the inner layer further comprises a baseand the base is selected from the group consisting of a hydroxide base,alkali metal bicarbonate, alkali metal carbonate, alkali metalphosphate, alkali metal citrate, or physiologically tolerated amine. 37.The formulation of claim 1, wherein the inner layer further comprises abase and the base is a hydroxide base.
 38. The formulation of claim 1,wherein the inner layer further comprises a base and the base is sodiumhydroxide.
 39. The formulation of claim 1, wherein the pH dependentlysoluble polymeric material of the outer layer is a blend of at least twodifferent polymers having a pH threshold of about pH 6 and above. 40.The formulation of claim 39, wherein the at least two different polymersin the blend are different polymethacrylate polymers.
 41. Theformulation of claim 39, wherein there are the at least two differentpolymers in the blend in a ratio from about 40:60 to about 60:40. 42.The formulation of claim 1, wherein said pH dependently solublepolymeric material is present in the outer layer as a sole film formingpolymeric material.
 43. The formulation of claim 1, wherein said pHdependently soluble polymeric material is present in the outer layer inadmixture with a digestible polymeric material which is susceptible toattack by colonic bacteria.
 44. The formulation of claim 43, whereinsaid digestible polymeric material and said pH dependently solublepolymeric material are present in the outer layer in a ratio of up toabout 60:40.
 45. The formulation of claim 43, wherein said digestiblepolymeric material and said pH dependently soluble polymeric materialare present in the outer layer in a ratio from about 25:75 to about35:65.
 46. The formulation of claim 43, wherein said digestiblepolymeric material and said pH dependently soluble polymeric materialare present in the outer layer in a ratio from about 40:60 to about60:40.